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Fix corrupted files before the upload

  • Updated

Before you upload PDFs,  make sure they aren't structurally corrupted.

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Why a corrupted structure is not an A11Y violation (but still matters)?

Corrupted PDF structure is not an accessibility (A11Y) violation and is excluded from the PDF/UA standard. Instead, it falls under ISO 32000, section 7.5 which defines requirements for the general PDF file structure. We support both ISO 32000-1 and  ISO 32000‑2.

Although a corrupted file structure is not an accessibility issue, it still needs to be fixed. Some PDF readers may fail to open or properly process such files. While many readers ignore minor structural problems and display the document, this is not guaranteed in all tools or environments.

Thus, structurally corrupted PDFs are considered technically invalid, even if they appear to work in some readers.

Common causes of PDF corruption

The following table lists the common causes of PDF corruption:

Cause Details

Invalid or redundant data in the file

Extra non‑binary or unexpected content may be present due to the following reasons:

  • Manual edits made in a text editor.
  • Errors introduced during file creation.
  • Content appearing after the %EOF marker is a common sign.

Bugs or outdated PDF‑generation software

Some tools produce invalid PDFs due to bugs or outdated PDF specifications.

File damage during saving or transfer

The file may have been partially saved, truncated, or corrupted during upload, download, or transfer.

How to verify that a PDF file is corrupted?

The following table describes the methods you can use to detect a structurally corrupted file: 

Detection method Details

Platform scan results

The platform flags structural corruption. Unlike some third‑party tools, the platform attempts to continue A11Y scanning whenever possible, even if structural issues are present.

Note: If the issue is critical, the file might be marked as invalid and scanning may not be possible at all. 

The file can't be opened

If standard PDF readers cannot open the file, it's likely that the file is structurally corrupted.

Manual inspection

Advanced users can open the PDF in a text editor and look for unusual content. 

Note: Pay special attention to unexpected characters or data after the %EOF marker, which often indicates corruption.

How to fix corrupted PDF files?

The following table lists possible methods to fixing corrupted PDFs:

Method Details

Identify and fix the root cause

Investigate why corrupted files are being produced in the first place.
Common issues include outdated tools, internal software bugs, or manual file modification. Fixing the root cause prevents the same issue from recurring and avoids repeated scan failures.

Re‑save the file using a reliable PDF editor

Many PDF editors automatically repair non‑critical structural issues when a file is re‑saved.

  • More advanced tools, such as Adobe Acrobat, typically preserve PDF/UA metadata.
  • Simpler tools, including browser‑based PDF viewers, might remove PDF/UA metadata during re‑save.

Note: Verify the file after re‑saving it. If the PDF/UA metadata is removed, subsequent scans will report additional accessibility violations, making the issue immediately visible.

Submit the file for remediation

Submit your file remediation to our Level Access team. We can:

  • Repair structural issues
  • Address accessibility violations at the same time. 

Note: This service is not free. You might also contact Level Access for guidance without requesting full remediation.


 

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