Improve the visual quality of scanned PDF documents using FunPDF's Scanned PDF Enhancement tool.
What is PDF Enhancement?
PDF Enhancement improves the visual appearance of scanned documents through advanced image processing:
What It Does:
- Straighten tilted pages (auto-deskew) - Fix crooked scans and phone photos
- Remove background discoloration - Clean yellowing, stains, shadows
- Clean scanning artifacts - Remove speckles, dust spots, compression noise
- Oversample to 300 DPI - Improve low-resolution scans for printing
- Optimize file size - Balance quality and compression
What It Does NOT Do:
- Does NOT add text layer or OCR
- Does NOT make PDFs searchable
- Pure visual enhancement only
For searchable PDFs: Use Scan to Searchable PDF tool after enhancement.
Step-by-Step Guide
1. Upload Your Scanned PDF
Upload your scanned PDF to the FunPDF Editor:
Using Drag and Drop:
- Drag your scanned PDF into the editor window
- Drop it anywhere on the page
- File loads automatically
Using Upload Button:
- Click "Upload PDFs" or "Add files" button
- Select your scanned PDF (up to 200MB)
- Click "Open" to upload
Best for:
- Scanner output
- Mobile phone photos of documents
- Photocopies saved as PDF
- Old or damaged document scans
2. Select Enhancement Tool
- Open the Scanned PDF Enhancement tool from the right sidebar
- Or select it from the tools dropdown menu
- The enhancement settings panel appears
3. Manually Rotate Pages (If Needed)
If pages are upside-down or sideways:
- Click on page thumbnails in the file preview area
- Use rotation buttons to rotate 90°, 180°, or 270°
- Fix orientation before enhancement
Important: This tool does NOT have automatic page rotation. You must manually rotate pages using the preview area buttons.
4. Configure Enhancement Options
Auto Deskew (Checkbox)
What it does:
- Automatically straightens tilted or crooked pages
- Detects text/content angle and rotates to be perfectly straight
- Essential for phone photos and uneven scanner feeds
When to enable:
- Phone camera photos (almost always tilted)
- Documents fed unevenly through scanners
- Old crooked scans
- Any scan that looks tilted
Recommended: Enable for most scans
Remove Background (Checkbox)
What it does:
- Eliminates paper discoloration (yellowing from age)
- Removes coffee stains, water marks, shadows
- Cleans scanner bed dirt and noise
- Converts off-white/gray backgrounds to clean white
- Makes text darker and more readable
When to enable:
- Old documents with yellowed paper
- Stained documents (coffee, water)
- Poor lighting in phone photos
- Scanner bed dirt visible
- Damaged or aged documents
Caution: May affect intentional colored backgrounds
Clean Artifacts (Checkbox)
What it does:
- Removes scanning speckles (dust on scanner glass)
- Eliminates JPEG compression artifacts
- Cleans salt-and-pepper noise
- Removes fine scanning lines
- Results in crisp, professional-looking pages
When to enable:
- Low-quality photocopies with noise
- Scans with visible dust spots
- Noisy or grainy scans
- Thermal printer output with artifacts
⚠️ WARNING: May leave visual artifacts. Always review results carefully before using the enhanced PDF.
Oversample to 300 DPI (Checkbox)
What it does:
- Increases resolution of low-quality scans to 300 DPI
- 300 DPI is standard for high-quality printing
- Improves clarity and sharpness
- Increases file size
When to enable:
- Original scan has low resolution (below 300 DPI)
- Planning to print the document
- Need professional print quality
- Images look pixelated or blurry
When to skip:
- High-resolution scans already (300+ DPI)
- File size is a concern
- Only for digital viewing
Optimization Level (Dropdown)
None (0):
- No compression
- Largest file size
- Perfect quality
- Use when file size doesn't matter
Low (1):
- Slight file size reduction
- Near-perfect quality
- Large files
- Good for archival documents
Medium (2) - Recommended:
- Balanced quality and file size
- Very good quality maintained
- Reasonable file size
- Best for most use cases
High (3):
- Maximum compression
- Smallest file size
- Slight quality reduction (images slightly blurrier)
- Good for storage optimization or web use
5. Start Enhancement
Click "Enhance PDF" to begin:
Small Files (≤10MB):
- Process instantly on server
- Files not stored
- Results in seconds
Large Files (>10MB):
- Upload to secure temporary storage
- Process in background
- Real-time progress bar shows status
- Files auto-delete after 2 hours
- Can cancel processing if needed
6. Download Result
After enhancement completes:
- Click "Download" to save the enhanced PDF
- Compare with original to verify improvements
- Re-process with different settings if needed
- Keep original as backup
Enhancement Scenarios
Straighten Crooked Phone Photos
Settings:
- ✅ Auto Deskew: ON
- ✅ Remove Background: ON (to eliminate shadows)
- ⬜ Clean Artifacts: OFF
- ⬜ Oversample to 300 DPI: OFF
- Optimization: Medium
Result: Straight, clean document from phone photo
Clean Old or Stained Documents
Settings:
- ✅ Auto Deskew: ON
- ✅ Remove Background: ON (remove yellowing/stains)
- ✅ Clean Artifacts: ON (remove age spots)
- ⬜ Oversample to 300 DPI: Optional
- Optimization: Medium
Result: Clean white background, readable text
Improve Low-Quality Photocopies
Settings:
- ✅ Auto Deskew: ON
- ⬜ Remove Background: OFF
- ✅ Clean Artifacts: ON (remove noise)
- ⬜ Oversample to 300 DPI: OFF
- Optimization: Low
Result: Crisp, professional-looking copy
Prepare Scans for Professional Printing
Settings:
- ✅ Auto Deskew: ON
- ✅ Remove Background: ON
- ⬜ Clean Artifacts: OFF (preserve detail)
- ✅ Oversample to 300 DPI: ON (print quality)
- Optimization: None or Low
Result: Print-ready high-quality PDF
Pre-Process for OCR
Settings:
- ✅ Auto Deskew: ON (straight text = better OCR)
- ✅ Remove Background: ON (clean background = better OCR)
- ✅ Clean Artifacts: ON (clearer text = better OCR)
- ⬜ Oversample to 300 DPI: Optional
- Optimization: Medium
Result: 20-30% better OCR accuracy
Understanding Enhancement Effects
Auto Deskew
- Before: Tilted, crooked pages
- After: Perfectly straight, aligned text
- Side effect: None, safe to use always
Remove Background
- Before: Yellowed, stained, gray backgrounds
- After: Clean white background, darker text
- Side effect: May affect colored backgrounds, charts, images
Clean Artifacts
- Before: Noisy, speckled, grainy scans
- After: Crisp, clean, professional appearance
- Side effect: ⚠️ May leave visual artifacts in some cases
Oversample to 300 DPI
- Before: Low resolution, pixelated
- After: Sharper, print-quality resolution
- Side effect: Larger file size
Best Practices
Before Enhancement
Review Original:
- Identify main issues (tilt, stains, noise)
- Check if pages need manual rotation
- Determine which options are needed
Start Conservative:
- Enable only needed options
- Use medium optimization
- Test with one page first
During Enhancement
Test First:
- Process single page to preview results
- Verify settings produce desired effect
- Adjust if needed before processing entire document
Common Combinations:
- Phone photos: Deskew + Remove Background
- Old documents: All options except Oversample
- For OCR prep: Deskew + Remove Background + Clean Artifacts
After Enhancement
Verify Results:
- Compare result with original
- Check text remains readable
- Verify no important details removed
- Ensure quality meets needs
Next Steps:
Troubleshooting
Background Removal Too Aggressive
Problem: Important content removed or colors washed out
Solutions:
- Disable "Remove Background" option
- Use lower optimization level (1 or 2)
- Re-scan with better lighting if possible
- Keep original document colors if intentional
Text Looks Jagged or Blurry
Problem: Text appears rough or unclear after enhancement
Solutions:
- Disable "Clean Artifacts" (may be too aggressive)
- Use lower optimization level (1 or None)
- Original scan quality may be too low - re-scan at higher resolution
- Try without "Oversample to 300 DPI"
Page Orientation Still Wrong
Problem: Pages are upside-down or sideways after enhancement
Solutions:
- Manually rotate pages using rotation buttons in file preview area BEFORE enhancement
- This tool does NOT have automatic page rotation
- Check each page orientation before processing
- Re-process with correct rotation if needed
Clean Artifacts Left Visual Problems
Problem: Enhancement created artifacts or visual issues
Solutions:
- Re-process with "Clean Artifacts" disabled
- This option has a warning for a reason - may not work well for all scans
- Use higher quality original scan if possible
- Keep original if enhancement made things worse
File Size Too Large
Problem: Enhanced PDF is too large
Solutions:
- Increase optimization level to 2 or 3
- Disable "Oversample to 300 DPI" (significantly increases file size)
- Use Compress PDF tool after enhancement
- Consider if all enhancement options are truly needed
Enhancement Didn't Improve Quality
Problem: Result looks the same as original
Solutions:
- Original may already be high quality
- Enable more aggressive options (Remove Background, Clean Artifacts)
- Some scans may not benefit from enhancement
- Very poor quality scans may need re-scanning
Use Cases
Mobile Phone Photos
- Enable deskew to straighten
- Enable background removal for shadows/lighting
- Creates professional documents from phone photos
- Perfect for receipts, forms, contracts photographed on-the-go
Old or Damaged Documents
- Remove yellowing from aged paper
- Clean coffee/water stains
- Remove age spots and discoloration
- Preserve historical documents digitally
Low-Quality Photocopies
- Clean noise and speckles
- Improve readability
- Make text crisp and clear
- Professional output from poor copies
Pre-Processing for OCR
- Always enhance BEFORE OCR
- Clean, straight scans = 20-30% better OCR accuracy
- Remove noise for better text recognition
- Essential for best searchable PDF results
Professional Printing
- Oversample to 300 DPI for print quality
- Clean backgrounds for professional appearance
- Straight pages for neat printing
- Archival-quality output
When to Use Enhancement
✅ Use Enhancement When:
- Scans are tilted or crooked
- Pages have stains, yellowing, discoloration
- Old documents with aged paper
- Low-quality photocopies with noise
- Phone photos of documents
- Preparing for OCR (significantly improves accuracy)
- Need professional-looking output from poor input
⬜ Skip Enhancement When:
- Scan quality already excellent
- PDF already contains text layer (use OCR tools instead)
- Document has intentional colored backgrounds
- Preserving exact original appearance is critical
- Artistic or photographic content (not text documents)
Privacy and Security
Small Files (≤10MB)
- Process on server without storage
- Not stored
- Immediate results
- Maximum privacy
Large Files (>10MB)
- Temporarily stored during processing
- Automatically deleted after 2 hours
- Secure temporary storage
- Files don't stay permanently
See Is My Data Secure? for full privacy details.
Next Steps
Start improving your scanned PDFs with Scanned PDF Enhancement now!