Darken PDF

Darken faint signatures, pale ballpoint ink and washed-out scans so they print clearly. Boost contrast, thicken strokes and clean up grey paper — entirely on your device.

About this tool

Darken PDF — Make Faint Signatures and Pale Scans Print Clearly

Darken faint ballpoint signatures, pale handwriting and washed-out scans so the printout is readable. Compare before and after, then download or print — the PDF never leaves your browser.

Made for Faint Signatures

Light-blue ballpoint barely registers in brightness, so Toolula measures ink by its darkest colour channel. Faint strokes get denser while the signature keeps its blue — or switch to grey or black & white for the crispest print.

Clean Paper, Thicker Strokes

Grey, yellowed or shadowed paper is evened out to white first, so only the writing gets darker. Thicken strokes by one to three pixels when a signature still looks thin on paper.

Just the Signature, or Whole Pages

Toolula suggests where the signatures are; accept them or drag a box yourself, and only those spots get darker while the rest of the page, its text included, stays as it was. Without marked areas, darken all pages or only the ones you choose.

How to use it

  1. Drop the PDF with the faint writing. Toolula looks for signatures and shows its suggestions as dashed amber boxes.
  2. Accept a suggestion with ✓, ignore the rest, or drag a box around a signature yourself. Without boxes, choose all pages or only some.
  3. Pick a preset (faint signature, faded print or fax, pencil) or set darkening, contrast and stroke thickness yourself.
  4. Drag the before/after divider and zoom in to check the result.
  5. Click Darken PDF, then download or print the copy. Keep the original file: the darkened version is meant for printing.

Frequently asked questions

Will my text still be selectable?

With marked areas, yes: only those spots get a darkening layer and the page text stays selectable. When whole pages are darkened, they are saved as images at 150–300 DPI and their text can no longer be selected or searched. Pages you leave out stay untouched.

Which output should I choose for printing?

Black & white gives the sharpest, smallest print and suits faxes and plain text. Colour keeps a blue signature blue, which helps tell the original from a copy. Grey sits in between and works well for pencil.

Are my contracts uploaded to a server?

No. Toolula processes the document inside your browser tab with pdf-lib and WebAssembly, so the file never leaves your device.

Is it really free?

Yes. You can use every Toolula PDF tool for free, without an account. The free plan has fair-use limits; Toolula Pro, an optional plan, raises them and adds advanced features.