What Is a PDF? Common PDF Problems and How to Solve Them
· 7 min read · Education
What Is a PDF?
PDF (Portable Document Format) was created by Adobe Systems in 1993 and became an open ISO standard (ISO 32000) in 2008. The format's core promise is fidelity: a PDF should look exactly the same on every device, operating system, and screen size — unlike Word documents, which reflow depending on the application version, fonts installed, and page margin settings.
What a PDF File Contains
- Text with embedded font data (so the correct typeface renders even if the font isn't installed on your device).
- Vector graphics — lines, shapes, and fills that scale without quality loss.
- Raster images — photos, scans, and screenshots stored at fixed resolution.
- Interactive elements — forms, hyperlinks, and bookmarks.
- Metadata — author, creation date, software used.
- Optional: digital signatures, encryption, and embedded files.
Why Do PDF Files Get Corrupted?
PDF corruption is more common than most people realise. Common causes include:
- Interrupted download — browser closed or internet connection dropped mid-download.
- Incomplete email attachment transfer — email servers sometimes truncate large attachments.
- File saved during a system crash or power cut, leaving the internal structure incomplete.
- Editing with incompatible software that writes invalid PDF structure.
- Storage media corruption — failing hard drives or damaged USB drives.
A corrupted PDF typically shows a blank page, renders only partial content, or throws a "file is damaged and cannot be repaired" error.
How to Fix a Corrupted PDF
- Try a different PDF reader — Chrome's built-in viewer, Firefox, or Adobe Acrobat handle some broken files better than others.
- Re-download the file — if you received it via email or a web link, ask the sender to resend it.
- Use MagPDF's Compress PDF tool — it rebuilds the PDF's internal structure using pikepdf, which can repair mild structural corruption.
- For scanned PDFs with garbled or unreadable text, run MagPDF's OCR tool to re-extract readable text from the page images.
Why Is My PDF Password Protected and How Do I Open It?
PDF files can be encrypted with a password so only authorised recipients can open them. If you receive a password-protected PDF and know the password, simply enter it when prompted by your PDF reader. If you created the file yourself and forgot the password, use MagPDF's Unlock PDF tool — you will still need to provide the original password, as AES-256 encryption cannot be bypassed. If the file was sent to you and you don't have the password, contact the sender.
Why Are Some PDFs So Large?
Scanned pages are stored as bitmap images (each A4 page at 300 dpi is roughly 3–6 MB uncompressed), embedded fonts add overhead, and some export tools include redundant metadata. Use MagPDF's Compress PDF tool to reduce file size before emailing or uploading. See our full guide on PDF compression for expected reduction figures by file type.
Common PDF Problems and Their Solutions
| Problem | Likely Cause | Solution |
|---|---|---|
| PDF opens blank | Corrupted or DRM-locked file | Try re-downloading or opening in a different PDF reader |
| Text is not selectable | Scanned document (image-only) | Use MagPDF OCR to extract selectable text |
| PDF is too large to email | Uncompressed images or scanned pages | Use MagPDF Compress PDF |
| Pages are sideways | Incorrect page rotation saved in file | Use MagPDF Rotate PDF |
| File is password-locked | Encrypted by the sender | Use MagPDF Unlock PDF (requires password) |
| Merged PDF has wrong page order | Files uploaded in wrong order | Use MagPDF Merge PDF with drag-to-reorder |