Enhance scanned PDF
Tune contrast and readability on scanned pages.
Makes scanned pages easier to read by changing brightness and contrast, or converting them to grayscale or pure black and white.
How to use it
- Open Enhance scanned PDF in superPDF.
- Choose a document, or pick one saved in My documents.
- Enter the pages to use, or leave the field empty to use every page.
- Set the options described below.
- Select Adjust pages, check the result, then download it.
Options
| Option | Values | Default |
|---|---|---|
| Pages | Page numbers or ranges, for example 1, 3-5 | All pages |
| Brightness (-100 to 100) | Number | 0 |
| Contrast (-100 to 100) | Number | 20 |
| Color | One of color, grayscale, black and white | color |
| Black-and-white threshold (0 to 255, higher is darker) | Number | 160 |
The black-and-white threshold sets how dark a pixel must be to turn black: raise it if faint text disappears, lower it if the background turns grey or speckled.
Output
A new PDF in which each adjusted page is a single image of the same size. Pages you leave out are unchanged.
Adjusted pages become images
Each page you adjust is redrawn at 200 dpi and replaced by a single image of the same size, so its text and vector drawings become pixels. Use OCR PDF on those pages to make the text searchable again. Page size and rotation stay the same, and links and comments on adjusted pages are kept.
Black and white pages are stored as 1-bit images, which are usually much smaller than the original scan. Color and grayscale pages are stored as JPEG. Pages are not straightened (deskewed).
Long documents
Pages are adjusted one at a time, so a document of thousands of pages works without filling your computer’s memory. While it runs you see the page it is on and about how long is left. Select Cancel to stop: your file is not changed. Adjusted pages and the result are kept in your browser’s storage on this device until you run the tool again, and are never uploaded.
Limits
No file size or page limit. Everything runs on your device, so very large files are fastest on a computer.
Privacy
Runs in your browser. Your files are processed on your device and never uploaded.