[Feature Request]: migrate pdf-lib to pdfium for measurement scales

[Frooodle]

Feature Description

EmbedPdfViewer.tsx::extractPageMeasureScales dynamically imports pdf-lib for the ruler tool
see if it spossible to migrate and that we can grab /Measure data

Why is this feature valuable?

No response

Suggested Implementation

No response

Additional Information

No response

No Duplicate of the Feature

• I have verified that there are no existing features requests similar to my request.

[web-dev0521]

Hi @Frooodle,

Thank you for raising this! I looked into migrating extractPageMeasureScales in EmbedPdfViewer.tsx from @cantoo/pdf-lib to @embedpdf/pdfium and wanted to share some findings before diving in.

The /Measure data we need lives deep in the PDF structure tree:
Page → /VP (array) → Viewport dict → /Measure dict → R / D / X / C / U

Reading it requires walking arbitrary PDF dictionary and array objects, which means we need APIs like:

• FPDF_GetPageDictionary
• FPDF_Dictionary_GetObjectFor
• FPDF_Array_GetObjectAtIndex
• FPDF_Object_GetFloat
• FPDF_Object_GetString
• FPDF_Object_GetType

After checking the full functions.d.ts type declarations in the @embedpdf/pdfium WASM module, unfortunately none of those low-level PDF object traversal APIs appear to be exposed. The module's public surface is focused on higher-level operations like rendering, annotations, form fields, and page geometry — not the raw PDF object model.

@cantoo/pdf-lib happens to be a really good fit for this specific task, and since it's already loaded via a dynamic import (lazy), it doesn't contribute to the initial bundle. The comment at the top of pdfiumService.ts even acknowledges that some modules with legitimate low-level PDF structure needs are expected exceptions.

A couple of possible paths forward:

• Keep pdf-lib for extractPageMeasureScales and document it as an intentional exception.
• File an upstream feature request against @embedpdf/pdfium to expose dictionary traversal APIs — if that lands, the migration becomes straightforward.

Happy to discuss further or help in any other way!