PDF: a PDF/A-2b file at PDF 1.4 writes long pages as PDF 1.6 with a UserUnit

PDF/A-2 limits page boundaries to 14,400 units (ISO 19005-2, 6.1.13), and
PDF 1.4 has no UserUnit. A PDF/A-2b export at PDF 1.4 with a page longer
than 14,400 pt was written in points, with a MediaBox over 14,400 units,
whether or not longPagesInPoints was on.

Such a file is now written as PDF 1.6 with a UserUnit and a warning that
names the version, as PDF 1.5 files already are. PDF/A-2 files may declare
PDF 1.0 to 1.7. Pages past 32,767 pt that aren't whole numbers of points
are written too, since the refusal applies only to PDF 1.3 and 1.4 files.
Files whose pages are all 14,400 pt or shorter stay PDF 1.4.

docs/mcp.md

@@ -874,7 +874,12 @@ export. PDF/X-1a and PDF/X-3 files are PDF 1.3 files too.
 A page with a side longer than 14,400 pt is written with a `UserUnit` (PDF 1.6): its longer side divided by 14,400,
 rounded up to the next thousandth, with the page's sizes and coordinates in those units, so that no side is longer than
 14,400 units (ISO 32000-1, Annex C.2). A PDF 1.5 file with such a page is written as PDF 1.6, with a warning, and
-keeps PDF 1.5's encryption (128-bit RC4). PDF/X files and PDF 1.3 and 1.4 files write such a page in points, and apps
+keeps PDF 1.5's encryption (128-bit RC4). A PDF/A-2b file at PDF 1.4 with such a page is written as PDF 1.6 too, with a
+warning, whether or not `longPagesInPoints` is on, so that its page boundaries stay within PDF/A-2's limit of 14,400 units
+unless the page is too narrow for that (below)
+([veraPDF rule 6.1.13-11](https://github.com/veraPDF/veraPDF-validation-profiles/wiki/PDFA-Parts-2-and-3-rules#rule-6113-11);
+PDF/A-2 files may declare PDF 1.0 to 1.7, [rule 6.1.2-1](https://github.com/veraPDF/veraPDF-validation-profiles/wiki/PDFA-Parts-2-and-3-rules#rule-612-1)).
+PDF/X files and other PDF 1.3 and 1.4 files write such a page in points, and apps
 that keep to the limit cut it to 200 in. `longPagesInPoints: true` (off by default; "Write pages longer than 200 in at
 full size in points" in the Save PDF dialog's General section) writes such a page in points at every PDF version, without
 a `UserUnit`, and a PDF 1.5 file stays PDF 1.5; the warning then says the page is written in points. In PDF 1.3 and 1.4 files, PDF/X-1a and PDF/X-3 among them, a real number can

docs/target-app-parity.md

@@ -1443,6 +1443,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
     In a `.ai` opened from its editing data, Bas Relief in an art style takes its Detail, Smoothness and Light direction from the style's settings block, and an object other than type with it opens as itself with the live effect. A settings block that VectorCraft can't read (malformed, another effect's, a value out of range or a key it doesn't know) keeps the object's drawn look (part of #637; [raster effects reference](https://helpx.adobe.com/illustrator/desktop/special-effects-styles/apply-filter-effects/raster-effects-reference.html), [Photoshop File Formats Specification](https://www.adobe.com/devnet-apps/photoshop/fileformatashtml/), [scripting the filter gallery](https://community.adobe.com/questions-712/scripting-support-for-the-filter-gallery-1064646); `crates/eps/src/import/ai/style/tests.rs`, `crates/eps/src/import/ai/tests.rs`).
     PDF export and `.ai` saves write a page with a side longer than 14,400 pt with a `UserUnit` (PDF 1.6), its longer side divided by 14,400 and rounded up to the next thousandth, so that no side is longer than 14,400 units (ISO 32000-1, Annex C.2); a PDF 1.5 file with such a page is written as PDF 1.6 with PDF 1.5's encryption, PDF/X files and PDF 1.3 and 1.4 files write it in points (in PDF 1.3 and 1.4, a page past 32,767 pt that needs a real number past 32,767 is refused with an error naming it), a page whose short side is 3 pt or longer but would be under 3 units at that `UserUnit` gets a smaller one that keeps the short side at 3 units, and the export's warnings give each such page's size and how it is written (#6382). The Save PDF dialog's "Write pages longer than 200 in at full size in points" (`longPagesInPoints`, off by default) writes such pages in points without a `UserUnit` at every PDF version.
     PDF export warns when a PDF/X file has no bleed on a side where the document's bleed has one, and writes the file as asked.
+    A PDF/A-2b export at PDF 1.4 with a page longer than 14,400 pt is written as PDF 1.6 with a `UserUnit` and a warning, whether or not `longPagesInPoints` is on, so its page boundaries stay within PDF/A-2's limit of 14,400 units (ISO 19005-2, 6.1.13) unless the page is too narrow for that (`crates/pdf/src/tests/marks.rs`).
     PDF/X-1a, PDF/X-3 and PDF 1.3 files keep the art under the hidden part of a picture, gradient, pattern, mesh or raster effect that a clipping mask or clipping layer crops: flattening rasterizes only the part of such art that its clipping path shows, on its own page and on the next one. Layers the file leaves out are left out of the flattening, and transparent art that a clipping path hides entirely is removed (`crates/engine/src/cmd/fileio/tests_pdfx.rs`).
     Placed (linked) files in a `.ai`'s editing data come in as linked images in their place, each showing the low-resolution preview the file keeps of it until its file is found or relinked in the Links panel (a file found next to the document, at its path, or in the folder the editing data names relative to the document's, such as `src/`, is read as the document opens, and its link takes that file's size, modification time and hash). A file with them no longer falls back to its PDF part, so its guides, sublayers and hidden objects open (#1264; `crates/eps/src/import/ai/tests.rs`, `crates/engine/src/tests/links.rs`). In a file opened that way, a gradient with stops in the middle runs its whole ramp across its shape and a gradient object no longer passes its fill to the next path (#1390); text objects with an appearance keep their own text and frame, type of hidden layers stays hidden, and type on later artboards lands on its text objects (#1391); area type whose frame is too short for a line of the fallback font shows its first line, the frame made taller with a warning in the open result (#1392).
     Placed (linked) files in a `.ai`'s editing data come in as linked images in their place, each showing the low-resolution preview the file keeps of it until its file is found or relinked in the Links panel (a file found next to the document or at its path is read as the document opens). A file with them no longer falls back to its PDF part, so its guides, sublayers and hidden objects open (#1264; `crates/eps/src/import/ai/tests.rs`, `crates/engine/src/tests/links.rs`). In a file opened that way, a gradient with stops in the middle runs its whole ramp across its shape and a gradient object no longer passes its fill to the next path (#1390); text objects with an appearance keep their own text and frame, type of hidden layers stays hidden, and type on later artboards lands on its text objects (#1391); area type whose frame is too short for a line of the fallback font shows its first line, the frame made taller with a warning in the open result (#1392).