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🛠️ Fix the “This PDF uses an unsupported format” error in Ugosign

Learn how to fix the “This PDF uses an unsupported format” error in Ugosign. Step-by-step guide to ensure PDF compatibility and successfully sign your documents.

🎯 Objective

Fix the “This PDF uses an unsupported format” error in order to open, preview, or send the document for signature in Ugosign.

📝 Prerequisites

  • A PDF file showing an error during upload (compressed, optimized, encrypted, or non-standard PDF)
  • A PDF conversion or repair tool (e.g. Adobe Acrobat, LibreOffice, PDF-XChange, or an online service)
  • An active Ugosign account

📍 Steps

🌐 Online method (ILovePDF)

  1. Go to the ILovePDF website, section Repair PDF .
  2. Upload the PDF file that shows the error.
  3. Click “Repair PDF” and wait a few seconds.
  4. Download the repaired PDF file to your computer.
  5. Upload the repaired file again in Ugosign .
  6. Check that the document opens correctly and the error is gone.

💻 Local method (command line)

This method recreates a more compatible PDF using the Ghostscript tool.

1. Install Ghostscript

2. Run the conversion command

In a terminal, run the following command:

gs \
 -sDEVICE=pdfwrite \
 -dCompatibilityLevel=1.4 \
 -dPDFSETTINGS=/default \
 -dNOPAUSE -dQUIET -dBATCH \
 -sOutputFile=pdf_fixed.pdf \
 pdf_original.pdf
  1. Upload the corrected PDF file in Ugosign .
  2. Verify that the document displays correctly.

🖥️ Local method (graphical interface)

Adobe Acrobat

  • Open the PDF document in Adobe Acrobat
  • File → Save As → Optimized PDF
  • Disable:
    • advanced compression
    • web optimization
  • Save the document again

LibreOffice

  • Open the PDF with LibreOffice
  • Export the document again as a PDF
  • During export, select:
    • PDF 1.4 compatibility
    • No advanced optimization or compression

✅ Expected result

The PDF opens without errors in Ugosign and can be previewed or sent for signature normally.

💡 Good to know

  • Encrypted or password-protected PDFs are not supported.
  • PDFs generated by banking, HR, or signature tools may require conversion.
  • The PDF/A format is recommended for optimal compatibility.
  • Files larger than 50 MB may also cause upload errors.
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Last update : 30 January 2026

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