e-Ink Reader Optimizer
Turns every page of a PDF into a black-and-white picture with a white background and, if you want, thicker strokes, for reading on e-ink screens.
About This Tool
e-Ink Reader Optimizer redraws every page of a PDF as a black-and-white picture. For each page it works out a brightness level automatically (the Otsu method): pixels darker than that level become black and the rest become white, which usually turns the grey background of a scan white. It is meant for scanned books and handouts that look faint on e-ink readers.
Two settings change the result. The slider marked "(Otsu Offset)" shifts the level: positive numbers turn more of the page black, which keeps faint strokes but can blacken shadows, and negative numbers turn more of it white. The buttons under "(Text Dilation)" thicken everything black by one or two pixels on every side. The before-and-after panel shows sample text, not your document, so download the result to judge it.
The new file holds pictures only, one JPEG per page at 144 pixels per inch. Text can no longer be selected or searched, and links, bookmarks and form fields are not carried over. Photos and shaded drawings lose their greys. The file is not guaranteed to be smaller and can be larger than the original. Everything happens in your browser; the file does not leave your device.
How to Use
Upload the PDF
Choose one PDF, for example a scanned book whose pages look grey or faint.
Adjust the Two Settings
Leave "(Otsu Offset)" at 0 to begin with. Move it to a positive number if thin strokes break up or vanish, or to a negative number if the background is not clean; go in small steps, because a large positive number can turn a grey page black all over. Under "(Text Dilation)" choose "Original ink", "Micro-Bold (1px)" or "Strong-Bold (2px)".
Convert and Download
Click "Optimize & Bold Text" and wait while each page is processed, then click "Download". To try other settings, change them and run it again.
Use Cases
Faint Scans of Old Books
Thin, pale letters usually come out solid black on white, and the bold buttons thicken the strokes further; very faint strokes may need a positive offset.
Photocopies With a Grey Background
The grey of a photocopied handout or exam sheet is usually pushed to white, leaving the text black.
Text Pages for a Black-and-White Reader
It suits pages that hold only text or line drawings. Pages with photographs lose their detail, because every pixel becomes either black or white.
Frequently Asked Questions
Does the file get smaller?
Not necessarily. Each page is stored as a JPEG picture, so a PDF made of real text can grow, while a heavy colour scan may shrink. The page shows the size of the result on the download button; compare it with your original.
Can I still select text, search or click links in the result?
No. Every page becomes a picture, so the text cannot be selected, searched or copied, and the links, bookmarks and form fields of the original are gone. Keep the original file if you need any of these.
Does the before-and-after panel show my document?
No. It shows the same sample text on both sides, and the only thing that changes in it is the weight of the sample when you pick a bold option. Nothing on the screen previews your pages. On the slider, above zero means more black and below zero means more white.