Acrobat Preflight font invalid problem

Question

I am experiencing an issue when exporting PDFs from InDesign using the PDF/X-4 standard.

When running a Preflight check in Acrobat, the font Jost (downloaded from Google Fonts) is flagged as invalid. This issue occurs not only in my files, but also when I edit InDesign documents created by other designers who have used the same font. Additionally, several of my colleagues are encountering the same problem across different documents.

Here are the solutions I have already tried, none of which consistently resolve the issue:

Reinstalling the Jost font
Installing a clean version (both static and variable versions tested)
Removing older versions of the font before reinstalling
Clearing Adobe font cache files (AdobeFnt*.lst)
Outlining the text
Verifying that there are no transparency or color issues
Comparing content in Acrobat (no visible differences when flagged)
Checking for transparency issues (none found)
Ensuring consistent structure and formatting across pages
Setting font subsetting to 0% (sometimes works, but not consistently)
Exporting the PDF while packaging the file (sometimes works, but not consistently)
Restarting InDesign and re-exporting (sometimes works, but not consistently)
Testing with alternative fonts - issue does not occur with other fonts

The issue appears inconsistently, but frequently enough to disrupt workflow, and seems tied specifically to the Jost font and its handling in PDF/X-4 exports.

Could you please advise on what might be causing this issue and how it can be reliably resolved?

Thank you in advance for your help.

Tariq Ahmad Dar · Answer

Hello,

Thank you for taking the time to document your findings in such detail. The steps you have already done are thorough and very helpful in narrowing down the scope of the issue.

Based on your observations, the behavior is specifically related to how the Jost font is processed during PDF/X-4 export, particularly given that other fonts do not exhibit the same issue and that the problem occurs inconsistently across files and users.

Your testing around subsetting, packaging, and font reinstallation is especially valuable, and helps rule out common causes such as font corruption or caching.

At this point, this may be related to how certain font variants, especially variable or recently updated font versions, are embedded or validated during export and subsequently interpreted by Acrobat Preflight.

We appreciate you sharing these insights, as they can help others encountering similar behavior. Providing a sample file and the specific Preflight profile being used would help further investigate whether this is a font-specific limitation or something that may require deeper review.

~Tariq

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