Troubleshooting Garbled Text and Missing Characters in PDF Embedder

Users of the PDF Embedder plugin sometimes report an issue where the text in their embedded PDFs appears garbled, scrambled, or displays strange characters instead of the correct text. This problem can be particularly prevalent with non-English languages or PDFs that use specific fonts. This guide will explain the common causes and provide steps to resolve the issue.

Why This Happens

Based on community reports and developer responses, this problem is typically not a fault of your specific WordPress installation but is related to the underlying technology, pdf.js, which is used to render the PDFs in the browser. The errors often relate to how font information, specifically CMaps (Character Maps), are loaded and processed. A common console error associated with this is: Error during font loading: The CMap "baseUrl" parameter must be specified...

Common Solutions

1. Check for a Plugin Update

This issue was notably introduced in a specific version (4.8.0) and subsequently fixed. The first and simplest step is always to ensure you are running the latest version of the PDF Embedder plugin. The development team has historically been quick to address these rendering bugs in updates.

2. Clear Caching

If multiple PDFs are embedded on a single page (like an archive or category page), a known bug in the pdf.js library can cause rendering conflicts, leading to garbled text. A strong caching mechanism on your site or server might be serving an old, corrupted version of the necessary font files. Clear your WordPress cache, any server-side cache (like Varnish or Redis), and your CDN cache (like Cloudflare) to ensure the latest JavaScript and font assets are being served.

3. Conflict Testing

While less common, a theme or plugin conflict can sometimes interfere with the JavaScript required to properly render the PDF. To test for this:

1. Temporarily switch your theme to a default WordPress theme like Twenty Twenty-Four.
2. Deactivate all other plugins besides PDF Embedder.

If the PDFs render correctly after this, reactivate your plugins one by one to identify the culprit. You can then seek an alternative plugin or contact its developer for support.

4. Investigate the PDF Source

Before embedding, verify that the PDF itself is not the source of the problem. Open it in a standalone desktop PDF reader like Adobe Acrobat Reader. If the text appears garbled there as well, the issue is with the file's creation, not the embedding process. Ensure the software used to create the PDF is exporting with all fonts properly embedded.

When to Seek Further Help

If you have tried the steps above and the issue persists, the problem may be more complex. The PDF Embedder team has acknowledged specific, hard-to-fix bugs in the underlying Mozilla pdf.js project that they aim to work around in future plugin releases. For urgent issues, you may need to temporarily use a different PDF viewer plugin while waiting for a permanent fix to be released.