Pdflib Errors Common

Common pdf-lib Errors: Diagnosis & Fixes

Non-font, non-loading errors. For font/encoding errors see pdflib-errors-fonts. For document loading errors see pdflib-errors-loading.

Quick Diagnostic Checklist

When pdf-lib code produces unexpected results, check these in order:

1. Missing await? — embedFont, embedPng, embedJpg, copyPages, save ALL return Promises
2. Y-coordinate wrong? — PDF origin is BOTTOM-LEFT, not top-left
3. Unsupported image format? — ONLY PNG and JPG are supported
4. Cross-document page copy? — MUST use copyPages() before addPage()
5. Form field not found? — Names are case-sensitive and fully qualified (dot-separated)
6. Color looks wrong? — rgb() takes 0.0–1.0, NOT 0–255
7. Drawing looks wrong? — drawEllipse uses xScale/yScale, drawLine uses thickness
8. Unexpected blank page? — save() adds one if document has zero pages
9. Form appearances changed? — save() auto-updates field appearances by default

Decision Tree: "My PDF Output Looks Wrong"

PDF output is wrong
├── Content is missing entirely
│   ├── Used embedFont/embedPng without await? → See §1
│   ├── Copied page without copyPages()? → See §4
│   └── save() returned empty bytes? → Check await on save()
├── Content is in wrong position
│   ├── Text/image appears at bottom instead of top? → See §2
│   └── Ellipse/circle shape is wrong? → See §11
├── Colors are wrong
│   └── Used 0-255 instead of 0-1? → See §6
├── Form fields don't work
│   ├── "No field with name X" error? → See §5
│   ├── Duplicate field name error? → See §7
│   └── Field appears empty until clicked? → See §9
├── Merged PDF has issues
│   ├── Error when adding page from another doc? → See §4
│   └── copy() lost form fields/bookmarks? → See §8
└── Unexpected extra page
    └── Empty document got blank page on save? → See §10

§1 Forgotten await on Async Methods

Severity: CRITICAL — Most common cause of "everything breaks silently."

These methods return Promise — you MUST await them:

Broken:

const font = pdfDoc.embedFont(StandardFonts.Helvetica);
page.drawText('Hello', { font }); // font is a Promise, NOT a PDFFont!

Fixed:

const font = await pdfDoc.embedFont(StandardFonts.Helvetica);
page.drawText('Hello', { font });

ALWAYS use await on every embed*, copy*, save*, and load call.

§2 Coordinate System Confusion (Bottom-Left Origin)

Severity: HIGH — PDF uses bottom-left origin. HTML/CSS/Canvas uses top-left.

Broken:

// Developer expects y=50 to be near the top
page.drawText('Title', { x: 50, y: 50 }); // Appears near BOTTOM

Fixed:

const { height } = page.getSize();
page.drawText('Title', { x: 50, y: height - 50 }); // Near TOP

ALWAYS subtract from page.getSize().height when positioning from the top. NEVER assume y=0 is at the top of the page.

§3 Unsupported Image Formats

Severity: HIGH — pdf-lib supports ONLY PNG and JPG. No GIF, BMP, SVG, WebP, or TIFF.

There is NO embedImage(), embedGif(), embedBmp(), or embedSvg() method.

Fix: Convert images to PNG or JPG before embedding using an external library (e.g., Sharp, Canvas API, or browser canvas).

ALWAYS convert non-PNG/JPG images before passing to pdf-lib. NEVER attempt to pass GIF, SVG, BMP, or WebP bytes to embed methods.

§4 Cross-Document Page Addition Without copyPages()

Severity: CRITICAL — Pages from one document CANNOT be added directly to another.

Broken:

const sourcePage = sourceDoc.getPage(0);
targetDoc.addPage(sourcePage); // THROWS ERROR

Fixed:

const [copiedPage] = await targetDoc.copyPages(sourceDoc, [0]);
targetDoc.addPage(copiedPage);

ALWAYS call copyPages() on the TARGET document first. ALWAYS addPage() or insertPage() each copied page — copyPages() alone does NOT add them.

§5 Form Field Not Found (Case-Sensitive, Fully Qualified Names)

Severity: HIGH — Field names are case-sensitive and use dot-separated hierarchical names.

Broken:

form.getTextField('name'); // Throws if actual name is "form.personal.Name"

Fixed:

// ALWAYS enumerate fields first to discover exact names
const fields = form.getFields();
fields.forEach(field => {
  console.log(`Type: ${field.constructor.name}, Name: "${field.getName()}"`);
});
// Then use the exact name from enumeration
const nameField = form.getTextField('form.personal.Name');

ALWAYS enumerate fields with getFields() before accessing by name. NEVER guess field names — they are case-sensitive and may include parent prefixes.

§6 Color Values: 0.0–1.0, NOT 0–255

Severity: MEDIUM — All color functions use normalized 0.0–1.0 range.

Broken:

const red = rgb(255, 0, 0);   // Creates white/unexpected color
const gray = grayscale(128);   // Wrong

Fixed:

const red = rgb(1, 0, 0);         // Correct red
const gray = grayscale(0.5);       // Correct 50% gray
const teal = cmyk(1, 0, 0.5, 0);  // CMYK also uses 0-1

ALWAYS use 0.0–1.0 for rgb(), cmyk(), and grayscale(). NEVER pass 0–255 values to color functions.

§7 Duplicate Field Name Errors

Severity: MEDIUM — Creating two form fields with the same name throws an error.

Broken:

form.createTextField('email');
form.createTextField('email'); // ERROR: duplicate name

Fixed:

form.createTextField('email_primary');
form.createTextField('email_secondary');

ALWAYS use unique names for every form field.

§8 copy() Does NOT Copy AcroForms or Outlines

Severity: MEDIUM — PDFDocument.copy() creates a shallow copy. Form fields (AcroForm) and bookmarks (outlines) are NOT included in the copy.

Impact: If you copy a document with forms, the copied document will have the pages but non-functional form fields.

Workaround: Re-create form fields on the copied document, or use copyPages() to selectively transfer pages instead.

NEVER rely on copy() to preserve form fields or bookmarks.

§9 save() Auto-Updates Field Appearances

Severity: MEDIUM — By default, save() calls form.updateFieldAppearances() automatically, which can change how fields look.

To prevent this:

const pdfBytes = await pdfDoc.save({
  updateFieldAppearances: false,
});

ALWAYS pass { updateFieldAppearances: false } to save() when you want to preserve existing field appearances exactly as they are.

§10 save() Adds Blank Page If Document Is Empty

Severity: LOW — Calling save() on a document with zero pages automatically inserts one blank page, because the PDF specification requires at least one page.

ALWAYS add at least one page before calling save() to avoid unexpected blank pages.

§11 Drawing Method Parameter Names

Severity: MEDIUM — Some drawing methods use non-obvious parameter names.

drawEllipse: Uses xScale/yScale, NOT width/height

Broken:

page.drawEllipse({ x: 200, y: 200, width: 100, height: 50 }); // width/height IGNORED

Fixed:

page.drawEllipse({ x: 200, y: 200, xScale: 100, yScale: 50 });

drawLine: Uses thickness, NOT borderWidth

Broken:

page.drawLine({ start: { x: 0, y: 0 }, end: { x: 100, y: 100 }, borderWidth: 2 }); // IGNORED

Fixed:

page.drawLine({ start: { x: 0, y: 0 }, end: { x: 100, y: 100 }, thickness: 2 });

ALWAYS use xScale/yScale for drawEllipse. ALWAYS use thickness for drawLine. NEVER use width/height for ellipses or borderWidth for lines.

§12 Keywords Setter/Getter Asymmetry

Severity: LOW — setKeywords() takes string[] but getKeywords() returns string | undefined.

pdfDoc.setKeywords(['pdf', 'invoice', 'report']);
const keywords = pdfDoc.getKeywords(); // Returns "pdf,invoice,report" (single string)
const keywordArray = keywords?.split(',') ?? []; // Parse back to array

ALWAYS split the return value of getKeywords() to get an array.

§13 Page Rotation: Multiples of 90 Only

Severity: LOW — Page rotation ONLY accepts multiples of 90 degrees.

page.setRotation(degrees(90));  // Valid: 0, 90, 180, 270
page.setRotation(degrees(45));  // NOT a valid page rotation

ALWAYS use 0, 90, 180, or 270 for page rotation. NEVER use arbitrary angles for page rotation (drawing rotation supports any angle).

Reference Files

• references/methods.md — API signatures for methods involved in common errors
• references/examples.md — Complete error reproduction and fix examples
• references/anti-patterns.md — Comprehensive catalog of mistakes with root causes