Working with scans
How do I improve the quality of a scanned PDF before I send it?
Run the scan through Enhance with Sharpen on and a little more contrast, switch text-only pages to grayscale or pure black and white, then make it searchable and small enough to upload. Blur, skew and missing resolution cannot be repaired after scanning.
Visa applications, university admissions, tax portals, bank forms and insurance claims all ask for the same thing in slightly different words: a clear, legible copy. The same goes for employers and landlords. Wherever you are, the scans that get sent back tend to be the ones that were too faint, too grey or too large.
Most of that can be fixed after the scan is made. Some of it cannot, and knowing which is which saves a second trip to the scanner.
What "good quality" means to the person receiving it
Nobody checking a scan measures its resolution. They open it and ask three questions:
- Can I read every word? Faint text, grey backgrounds and speckle are what make them squint.
- Is it straight and complete? A crooked page or a cut-off edge makes a document look unreliable.
- Did it upload? Many upload forms set a file-size limit, and a colour scan of ten pages can go over it.
What can be fixed afterwards
| The problem | The fix in Enhance |
|---|---|
| Text looks faint or washed out | Raise Contrast |
| The whole page is too dark or too light | Adjust Brightness |
| Letters look soft, as in most phone photos | Sharpen (on by default) |
| Grain or dots from a cheap scanner | Remove speckles |
| Yellowed or coloured paper | Grayscale |
| A typed form or letter with nothing in colour | Pure black & white |
Contrast starts at +10 and Brightness at 0. Both sliders run from −50 to +50.
What cannot be fixed
Being honest about this matters, because a tool that promises everything wastes the time you could have spent rescanning.
- Motion blur or an out-of-focus photo. Sharpening makes edges crisper; it cannot rebuild letters that were never in focus.
- Too little resolution. If the scan was captured small, small text is already broken into a few pixels. Nothing afterwards puts the missing detail back.
- A crooked page. Enhance does not straighten or crop. Whole pages turned sideways or upside down are a job for Rotate PDF, but a slight tilt stays.
- Missing edges. If a corner was outside the scanner glass, it is not in the file.
- Glare and heavy shadows. Brightness and contrast can soften uneven lighting, but a bright reflection over a line of text has erased that text.
If any of these is the problem and the paper is still in your hands, scan it again.
Step by step
- Open Enhance and choose the file. It accepts a scanned PDF, or a JPG, PNG or WebP photo of a page.
- Beside the settings you will see your original. This is not a live preview; it is the page you are trying to rescue, so you can judge what it needs.
- Choose the fixes from the table above, then press Enhance.
- Press Download. A PDF comes back as a PDF, with every page cleaned and each page kept at its original paper size. A photo comes back as a PNG.
Each page of a PDF is redrawn at 200 DPI, cleaned and put back. The work happens on our server, and the upload is deleted as soon as the cleaned file is built.
Start gently
The most common mistake is pushing everything to the maximum. A few rules of thumb:
- Try the defaults first. Sharpen plus a little contrast fixes most phone photos of documents.
- Keep colour when colour is the proof. A coloured stamp, seal, signature in blue ink or a photo on an ID card can matter to the person checking it. Pure black & white turns every pixel fully black or fully white, and a pale stamp can vanish completely.
- Use black & white only on plain text. On typed letters and forms it gives the cleanest, smallest result there is. On photographs it looks harsh.
- Remove speckles only if you see speckles. It slightly softens fine detail, which is why it is off by default.
One thing to know about typed PDFs
Cleaning a page means redrawing it as a picture. If the PDF already had real, selectable text in it, that text stays readable but can no longer be selected or searched. The tool tells you when this applies to your file. For a scan, which is already a picture, nothing is lost.
Clean first, then recognise, then shrink
If the file is going to an official portal, the order matters:
- Enhance the scan, so the text is as clear as it can be.
- Run OCR PDF if the recipient needs to search or copy the text. Recognition is noticeably more accurate on a clean page than on a grey, speckled one.
- Run Compress PDF last if the portal has a size limit. Grayscale and black & white pages are already much smaller than colour, so you may find you no longer need it.
Always check the portal's own instructions for its size limit and accepted formats before you upload. They differ from one office to the next, even within one country.
Common questions
Can Enhance fix a blurry scan?
It can make soft text crisper with Sharpen and faint text darker with Contrast. It cannot recover letters that were out of focus or captured at too low a resolution. For those, the only real fix is scanning again.
Will it straighten a crooked scan?
No. Enhance does not straighten or crop. Pages that are sideways or upside down can be turned with Rotate PDF, but a slight tilt remains.
Should I use grayscale or black and white?
Grayscale for anything with shading, photos, stamps or signatures. Pure black and white only for plain typed text, where it gives the cleanest and smallest result.
Does enhancing change the page size?
No. Each page is redrawn at 200 DPI and put back at its original paper size, so an A4 scan stays A4.
Why can I no longer select the text after enhancing?
Cleaning a page redraws it as an image. For a scan nothing changes, because it was already an image. For a typed PDF the words stay readable but stop being selectable. Keep your original if you need the text.
My cleaned scan is too large to upload. What now?
Try Grayscale or Pure black & white first, since both make pages much smaller. If it is still too big, run Compress PDF on the result.