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AnglinAI Docs

05 — Substrate and Production (`PRINT-SUBSTRATE`)

Status: Normative reference. Part of the Print Accessibility knowledge base (Issue #2852). Scope: The physical carrier — paper, finish, duplexing, binding, imposition — and the production/print-time transforms that silently destroy conformance our software worked to guarantee.

Sourcing honesty for this section. Almost nothing here is regulated. Paper weight, opacity, finish, and brightness are industry practice and low-vision consensus guidance, not law. The one item that is a hard requirement for our output is PRINT-SUBSTRATE-008 (print-at-100% / shrink-to-fit): a document that meets every point-size rule on screen fails the moment a driver scales it, and we can and must design against that. Treat SUBSTRATE-001..007, 009, 010 as guardrails and buyer’s-guidance we hand to whoever operates the physical printer; they are not thresholds a validator can assert against a PDF alone.

PRINT-SUBSTRATE-001 — Paper weight / opacity threshold to control show-through

Level: SHOULD Applies to: all documents Source: Commercial print / low-vision production practice (opacity, not basis weight, is the governing property) Source strength: industry practice Machine-checkable: no Validation: Physical — hold a duplex proof over the following printed page under normal room light; text/ink from the reverse side MUST NOT be legible enough to compete with the front. As a purchasing proxy, specify stock with an opacity rating ≥ 92% (TAPPI opacity) or ≥ 24 lb bond (≈ 90 gsm) for duplex text documents.

Duplex-printed documents SHOULD be produced on stock whose opacity prevents reverse-side show-through from interfering with reading; a nominal floor of 90 gsm / 24 lb bond, opacity ≥ 92% is a safe default for office and short-run production.

Rationale: Show-through raises the effective visual noise floor. Low-vision readers, who are already operating near their contrast threshold (see PRINT-COLOR-002), lose the margin first; ghosted reverse-side text can also defeat OCR if the page is later re-digitized as an alternate format. Implementation notes: Not assertable from a PDF — we do not know the substrate. Surface it as an advisory in the audit/ACR output whenever a document is duplex-imposed (PRINT-SUBSTRATE-004) or whenever our pipeline emits a print-ready artifact: “Print on ≥90 gsm / ≥92% opacity stock if duplexing.” The flipbook and screen-only surfaces are exempt (no substrate).

PRINT-SUBSTRATE-002 — Finish: matte vs gloss and glare for low-vision readers

Level: SHOULD Applies to: all documents Source: Low-vision reading practice; APH Research-Based Guidelines for the Development of Documents in Large Print notes white paper “produces glare in some cases” Source strength: consensus standard Machine-checkable: no Validation: Physical — under a directional light source, tilt the printed page; specular glare MUST NOT wash out text at normal reading angles. Specify matte / uncoated stock for body-text documents; reserve gloss/coated for photographic inserts only.

Body-text documents SHOULD be printed on matte or uncoated stock. Glossy and coated finishes SHOULD be avoided for reading matter because specular reflection creates glare that is disabling for many low-vision readers.

Rationale: Glare from coated stock scatters light into the eye and reduces effective contrast; it disproportionately harms readers with cataracts, corneal irregularity, or general light sensitivity — the same population large print serves. Implementation notes: Production-time only; advisory in the print-ready hand-off. No PDF-level check.

PRINT-SUBSTRATE-003 — Paper color and brightness

Level: SHOULD Applies to: all documents Source: APH large-print guidelines (paper section): white or ivory/antique-white/eggshell/pastel with black text; gray paper and gray text are never acceptable Source strength: consensus standard Machine-checkable: partial Validation: Physical for stock color. Machine-adjacent: an audit MAY flag body text set in gray (any neutral below full ink density) as a violation of the “no gray text” rule — that part is checkable in the source file even though paper color is not.

Documents SHOULD be printed with black text on white or warm off-white stock (ivory, eggshell, antique white, pastel yellow/pink). Gray paper MUST NOT be used, and gray text MUST NOT be used, in documents intended for audiences that may include low-vision readers.

Rationale: Warm off-white reduces the glare of bright white while preserving contrast; gray text/stock collapses the luminance range and is, per APH, “virtually indecipherable” for many low-vision readers. Excludes low-vision readers at the contrast threshold. Implementation notes: The gray-text half is enforceable in our tooling: the audit and tag-tree editor can flag body runs whose fill is a mid-gray. Paper color is a hand-off advisory. Note this reinforces PRINT-COLOR — do not restate the contrast math here.

PRINT-SUBSTRATE-004 — Duplex rules for readability and fidelity

Level: SHOULD Applies to: all documents Source: Production practice; interacts with PRINT-SUBSTRATE-001 (show-through) and PRINT-FORM-020 (duplex form hazards) Source strength: industry practice Machine-checkable: partial Validation: A tool CAN detect that content is laid out for duplex (even/odd margin mirroring, back-side form fields). Physical confirmation of registration and show-through is human.

When a document is duplexed, front/back registration SHOULD be maintained, inner (gutter) margins SHOULD be mirrored on facing pages, and stock SHOULD meet the opacity floor in PRINT-SUBSTRATE-001. Content that must be seen or completed (form fields, signatures) SHOULD NOT be placed only on reverse sides without a front-side cue.

Rationale: Readers miss reverse-side content; poor registration and thin stock compound the loss. Excludes readers who scan for content on the “obvious” side and low-vision readers fighting show-through. Implementation notes: Cross-reference PRINT-FORM-020 for the form-specific hazard (missed back-side fields, signature on the back). Our reflow/WeasyPrint lane controls margin mirroring; the preserve (“flyer”) lane inherits whatever the source did — flag, don’t rewrite.

PRINT-SUBSTRATE-005 — Stapling / binding / hole-punch encroachment on the text block

Level: SHOULD Applies to: all documents Source: Production practice Source strength: industry practice Machine-checkable: partial Validation: Checkable against the layout: the live text block MUST clear reserved binding zones. Default reserved zones: ≥ 12.7 mm (0.5 in) on the bound edge for stapling/perfect-bind; a three-hole-punch column with a ≥ 12.7 mm clear gutter (US-Letter spacing: centers at 9.5 mm, 108 mm, 206.4 mm from the top edge; A4 differs — 2- or 4-hole at 80 mm centers per ISO 838 — so reserve the correct pattern for the target page size).

Documents intended for stapling, binding, or hole-punching SHOULD reserve a clear gutter so that no text, form field, or essential graphic falls within the binding/punch zone.

Rationale: Punched or stapled-through text is unrecoverable on paper and cannot be zoomed. Excludes everyone; low-dexterity readers also cannot flatten a tightly bound gutter. Implementation notes: Our margin design (PRINT-SUBSTRATE-008 resistance measures) should set the bound-edge margin ≥ 12.7 mm by default. The audit can measure the distance from the text block to the page edge and flag sub-gutter layouts. Binding intent itself is not in the PDF — treat as a “if bound, then” advisory.

PRINT-SUBSTRATE-006 — Booklet imposition and reading-order impact

Level: SHOULD Applies to: all documents Source: Production practice Source strength: industry practice Machine-checkable: no Validation: Human — proof the folded, gathered booklet and confirm the reader’s page sequence matches logical reading order.

When a document is imposed as a saddle-stitched or folded booklet, the imposition SHOULD preserve logical reading order after folding and gathering, and page-pair spreads SHOULD be designed as spreads (no content orphaned across the fold).

Rationale: Imposition reorders physical sheets; a naive n-up impose can scramble reading order or split a table across a non-adjacent fold. Excludes readers relying on continuous sequence — there is no tag tree to fall back on once it is paper. Implementation notes: Imposition happens downstream of us in the RIP/printer, not in our PDF. This is a hand-off caution to whoever imposes. Do NOT emit reader-spreads from our pipeline as if pre-imposed unless explicitly asked.

PRINT-SUBSTRATE-007 — Letter / A4 page-size scaling trap

Level: SHOULD Applies to: all documents Source: Production practice / cross-format printing Source strength: industry practice Machine-checkable: yes Validation: Read the PDF MediaBox. If page size is US Letter (612×792 pt) it will be auto-scaled to fit A4 (595×842 pt) and vice-versa by most drivers unless the operator forces 100%. Flag any document whose declared page size does not match the target print region’s default (Letter in US, A4 elsewhere).

Documents SHOULD declare the page size matching their intended print region (US Letter for US distribution), because printing a Letter document on A4 (or the reverse) triggers automatic fit-scaling that shrinks type below its specified point size.

Rationale: A Letter→A4 auto-fit scales content to ~97% (width-limited: 595.28/612 ≈ 0.973), and A4→Letter is worse at ~94% (height-limited: 792/841.89 ≈ 0.941); an 18 pt large-print body silently becomes ~17.5 pt (or ~16.9 pt the other direction) and drifts out of conformance. This is PRINT-SUBSTRATE-008 arriving through the back door of a size mismatch. Excludes low-vision readers who were promised a point size they no longer receive. Implementation notes: Fully checkable. Our pipelines SHOULD emit Letter for US output and record the intended page size. The audit/ACR SHOULD flag a page-size/region mismatch as a scaling risk. Directly feeds the 008 resistance design.

PRINT-SUBSTRATE-008 — Print-at-100%: shrink-to-fit / fit-to-printable invalidates point-size rules

Level: MUST (for our output) Applies to: all documents Source: our-implementation rule (analytical; derived from how print drivers rasterize) Source strength: our-implementation rule Machine-checkable: yes Validation: (a) Every page’s MediaBox MUST be a real physical page size (Letter/A4/Legal), never an arbitrary or oversized box that forces fit-scaling. (b) The live text/field block MUST sit inside the printer’s unprintable-margin envelope — a ≥ 12.7 mm (0.5 in) margin on all four edges — so that “fit to printable area” has nothing to shrink. (c) Where the format allows, the document’s embedded print preferences MUST request actual size / 100% scale (PDF ViewerPreferences /PrintScaling /None). A validator asserts all three from the file.

Documents we generate MUST be designed so that printing at 100% requires no scaling: physical page size declared, all content held inside a ≥ 12.7 mm safe margin on every edge, and — for PDF — /PrintScaling /None set so the print dialog defaults to actual size. Point-size, form-geometry, and touch-target guarantees are only valid at 100%; a document that relies on the user selecting “Actual size” has no guarantee at all. Note /PrintScaling /None is an advisory viewer preference — some drivers, browser print paths, and OS dialogs ignore it — so it lowers risk but does not close it; the real page size and the safe-margin envelope are what make 100% printing survivable regardless.

Rationale: Default print behavior in Acrobat, Preview, Chrome, and most OS drivers is “Fit” / “Shrink oversized pages,” which scales the page down to clear the hardware’s unprintable border. Any content within ~4–6 mm of the edge triggers a global downscale of the entire page, dropping every specified point size, fill-space height, checkbox, and 44 px touch target below spec at once. This silently voids PRINT-TYPO, PRINT-FORM, and PRINT-ALT-001 in a single step. Excludes precisely the population every other rule protects — low-vision and low-dexterity readers — and it does so invisibly, because the on-screen document looked correct. Implementation notes: This is a hard gate on everything we emit:

  • Reflow / WeasyPrint lane: set @page { size: Letter; margin: 12.7mm; } (or A4 per region) as the floor; never allow content to bleed past it.
  • PDF preserve (“flyer”) lane: we usually cannot re-lay-out the source, but we CAN (1) verify the MediaBox is a real page size, (2) measure the content bbox against the 12.7 mm envelope and flag violations rather than silently accept them, and (3) inject /ViewerPreferences << /PrintScaling /None >> into the catalog so the print dialog defaults to 100%.
  • docx→AcroForm lane: inherit the WeasyPrint margin floor; ensure field widgets are inside the envelope (ties to PRINT-FORM-023 field-geometry validation).
  • Audit / ACR: report page-size sanity, edge-margin clearance, and presence of /PrintScaling /None as an explicit “print-at-100% resilience” check.
  • Tag-tree editor / flipbook: flipbook is screen-only (exempt); the editor should not move content into the unprintable envelope.

PRINT-SUBSTRATE-009 — N-up / multi-up scaling caution

Level: SHOULD Applies to: all documents Source: Production practice Source strength: industry practice Machine-checkable: no Validation: Human/operator — n-up (2-up, 4-up) is a print-dialog choice, not a document property; confirm the operator has not selected it for accessibility-critical output.

Accessibility-critical documents (large print, forms, any document with a declared minimum point size) SHOULD NOT be printed n-up / multiple-pages-per-sheet, because n-up scales each logical page down by 50% or more.

Rationale: 2-up halves the linear size of everything; a conforming 18 pt large-print page becomes ~9 pt. Same failure mode as 008 but operator-initiated. Excludes low-vision readers. Implementation notes: Not controllable from the file. Advisory in the print hand-off / large-print cover sheet: “Print one page per sheet, actual size.” No validator hook beyond the 008 checks.

PRINT-SUBSTRATE-010 — Bleed and safe areas

Level: MAY Applies to: all documents Source: Commercial print production practice Source strength: industry practice Machine-checkable: partial Validation: For commercially trimmed pieces: background color/imagery intended to reach the edge MUST extend ≥ 3 mm past trim (bleed), and no essential content SHOULD fall within ≥ 3 mm inside trim (safe area). Checkable if trim/bleed boxes are declared (TrimBox/BleedBox).

Documents destined for commercial trimming MAY declare bleed and safe areas; background elements meant to reach the edge SHOULD bleed ≥ 3 mm, and essential text/fields SHOULD stay ≥ 3 mm inside trim. This is production hygiene, not an accessibility requirement per se — but it prevents essential content being trimmed off.

Rationale: Trim variance (±1–2 mm) either shows a white sliver (no bleed) or shears essential content (no safe area). Only excludes readers if essential content is trimmed; otherwise cosmetic. Implementation notes: Only relevant for commercial-print output, which our pipelines rarely target. The 12.7 mm safe margin from PRINT-SUBSTRATE-008 already exceeds the 3 mm safe-area minimum, so meeting 008 satisfies this for our office/short-run output. Note the overlap; do not double-count.