PDF Conversion Issues

Troubleshoot common PDF conversion problems including file size errors, corrupt files, slow processing, and rendering issues.

PDF Conversion Issues

ZenFlip's conversion engine handles most PDFs without any issues, but occasionally you might run into problems. This guide covers the most common conversion issues and how to resolve them.

File Too Large

Symptom: You see an error message saying your file exceeds the maximum allowed size.

Cause: Each plan has a file size limit:

Plan

Max File Size

Explorer

50 MB

Creator

150 MB

Business

500 MB

Enterprise

Custom

Solutions:

  1. Compress your PDF - Use a tool like Adobe Acrobat's "Reduce File Size" or the free online tool SmallPDF to compress images and reduce overall size

  2. Lower image resolution - Re-export your PDF with images at 150 DPI instead of 300 DPI. This typically cuts file size by 50-70% with minimal visual impact.

  3. Split the document - Break a large PDF into multiple parts and create separate flipbooks for each

  4. Remove unnecessary pages - Delete any blank or filler pages before uploading

  5. Upgrade your plan - Move to a plan with a higher file size limit

Corrupt or Damaged PDF

Symptom: Upload fails immediately, or you see an error like "Unable to process this file" or "Invalid PDF."

Cause: The PDF file is damaged, uses a non-standard format, or was not fully generated.

Solutions:

  1. Re-export the PDF - Go back to the source application (InDesign, Word, Canva, etc.) and export a fresh PDF

  2. Try opening the PDF locally - If the PDF doesn't open in Adobe Acrobat or your browser's PDF viewer, the file is likely corrupt. Re-create it from the source.

  3. Check the file extension - Make sure the file is actually a PDF and not another format renamed to .pdf

  4. Use PDF/A format - Re-export using the PDF/A standard, which has stricter formatting rules and tends to produce more reliable files

  5. Repair the PDF - Adobe Acrobat Pro can sometimes repair damaged PDFs via File > Save As > Optimized PDF

Slow Conversion

Symptom: The conversion progress indicator has been running for a long time, or the status shows "Processing" for more than 10 minutes.

Cause: Several factors can slow down conversion:

  • Very large files (100+ MB)

  • High page count (200+ pages)

  • Complex vector graphics or illustrations

  • Heavy use of transparency effects

  • Embedded multimedia elements

Solutions:

  1. Wait a bit longer - Complex PDFs genuinely take more time. Conversion up to 15 minutes is normal for large or complex files.

  2. Check system status - Visit our status page to see if there's a known processing delay

  3. Reduce complexity - Flatten transparency effects and rasterize complex vector graphics before creating the PDF

  4. Reduce page count - Split large documents into smaller parts

  5. Try again - If the conversion appears stuck (no progress for 20+ minutes), cancel and re-upload the file. Occasionally a queue delay can cause longer-than-normal processing times.

Blank Pages in Flipbook

Symptom: Some or all pages appear white or blank in the flipbook, even though the PDF has content.

Cause: This usually happens due to transparency issues or unsupported PDF features.

Solutions:

  1. Flatten transparency - In your design application, flatten all transparency before exporting to PDF. In Adobe InDesign, use Edit > Transparency Flattener Presets.

  2. Rasterize the page - As a quick fix, "print" the PDF to a new PDF using a virtual printer, which rasterizes all content

  3. Check for embedded media - Video, audio, and 3D content embedded in PDFs cannot be converted. Remove these elements and re-export.

  4. Use RGB color space - Some CMYK-only PDFs with certain profiles can cause rendering issues. Convert to RGB before upload.

Missing or Incorrect Fonts

Symptom: Text appears in the wrong font, shows as squares or rectangles, or is completely missing.

Cause: The fonts used in the PDF are not embedded in the file.

Solutions:

  1. Embed all fonts - Re-export your PDF with font embedding enabled. In most applications, this is a checkbox in the PDF export options.

  2. Subset fonts - Use the "Subset fonts when percent of characters used is less than 100%" option to embed only the characters used, reducing file size.

  3. Convert text to outlines - As a last resort, convert all text to outlines/paths before exporting. This guarantees correct rendering but makes text non-selectable.

  4. Use common fonts - If font embedding is not possible, use widely available fonts like Arial, Times New Roman, or Helvetica.

Poor Image Quality

Symptom: Images in the flipbook look blurry, pixelated, or have compression artifacts.

Cause: Low-resolution images in the source PDF or heavy image compression.

Solutions:

  1. Use higher-resolution images - Ensure source images are at least 150 DPI at the size they'll appear in the PDF

  2. Reduce compression - When exporting to PDF, set image compression to Medium or High quality (JPEG quality 80-90%)

  3. Check original images - If the images look poor in the PDF before upload, they'll look poor in the flipbook too. Start with high-quality source images.

Conversion Fails Completely

Symptom: The conversion process ends with an error and no flipbook is generated.

Solutions to try in order:

  1. Re-upload the file - Sometimes a network hiccup during upload corrupts the file. Try uploading again.

  2. Re-export the PDF - Generate a fresh PDF from your source application

  3. Try a different PDF export preset - Use "High Quality Print" or "PDF/A" presets

  4. Simplify the PDF - Remove any interactive elements (form fields, annotations, multimedia) and try again

  5. Contact support - If none of the above works, email support@zenflip.io with the PDF attached (or a link to it if it's large). Our team can diagnose the specific issue.