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feat(page): add userUnit option for custom page units (PDF 1.6) #1676

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Merged
blikblum merged 3 commits into from
Jan 26, 2026
Merged

feat(page): add userUnit option for custom page units (PDF 1.6) #1676

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63d05dd
feat(page): add userUnit option for custom page units (PDF 1.6)
exoego Jan 25, 2026
97aaf65
Merge branch 'master' into feat-page-userunit
exoego Jan 26, 2026
8f9a9d6
Merge branch 'master' into feat-page-userunit
exoego Jan 26, 2026
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@
- Add pageLayout option to control how pages are displayed in PDF viewers
- Fix Interlaced PNG with indexed transparency rendered incorrectly
- Preserve existing PageMode instead of overwriting when adding outlines
- Add userUnit option for custom page units (PDF 1.6)
- Support outlines that jump to specific page positions with custom zoom level

### [v0.17.2] - 2025-08-30
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14 changes: 13 additions & 1 deletion docs/paper_sizes.md
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Expand Up @@ -83,6 +83,18 @@ In order to use the predefined sizes, the name of the size (as named in the list

// Passing size to the constructor
const doc = new PDFDocument({size: 'A7'});

// Passing size to the addPage function
doc.addPage({size: 'A7'});

### User Unit (PDF 1.6+)

The `userUnit` option allows you to scale the physical size of a page without changing the coordinate system. This is useful for creating large format documents like posters or banners that exceed the standard PDF coordinate limit (200 inches or 14400 points).

The default value is `1.0`, where 1 unit equals 1/72 inch (1 point). Setting `userUnit: 2.0` means 1 unit equals 2/72 inch, effectively doubling the physical size of the page.

// Create a page with 2x physical size
doc.addPage({ size: 'A4', userUnit: 2.0 });

// Create a large poster (4x scale)
doc.addPage({ size: [612, 792], userUnit: 4.0 });
2 changes: 2 additions & 0 deletions lib/page.js
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Expand Up @@ -74,6 +74,7 @@ class PDFPage {
this._options = options;
this.size = options.size || 'letter';
this.layout = options.layout || 'portrait';
this.userUnit = options.userUnit || 1.0;

// calculate page dimensions
const dimensions = Array.isArray(this.size)
Expand Down Expand Up @@ -107,6 +108,7 @@ class PDFPage {
MediaBox: [0, 0, this.width, this.height],
Contents: this.content,
Resources: this.resources,
UserUnit: this.userUnit,
});

this.markings = [];
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15 changes: 15 additions & 0 deletions tests/unit/page.spec.js
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@@ -1,6 +1,21 @@
import PDFDocument from '../../lib/document';

describe('page', function () {
describe('userUnit', function () {
test('defaults to 1.0', function () {
const doc = new PDFDocument();
expect(doc.page.userUnit).toBe(1.0);
expect(doc.page.dictionary.data.UserUnit).toBe(1.0);
});

test('can be set via page options', function () {
const doc = new PDFDocument({ autoFirstPage: false });
doc.addPage({ userUnit: 2.5 });
expect(doc.page.userUnit).toBe(2.5);
expect(doc.page.dictionary.data.UserUnit).toBe(2.5);
});
});

test('cascade page options', function () {
const doc = new PDFDocument({
autoFirstPage: false,
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1 change: 1 addition & 0 deletions tests/unit/trailer.spec.js
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Expand Up @@ -70,6 +70,7 @@ describe('Document trailer', () => {
/MediaBox [0 0 612 792]
/Contents 5 0 R
/Resources 6 0 R
/UserUnit 1
/Annots [9 0 R]
>>`,
]);
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