DarkenMyPDF

Features

One job, done properly: turn a faded or low-contrast PDF into one that prints clearly. Every control below exists because some real document needed it.

Processing modes

  • Auto Print Enhance

    Measures each page and applies only as much correction as it needs.

  • Print Ready

    Darker text, cleaner paper and stronger contrast, tuned for laser and inkjet output.

  • Darken Text

    Pushes faded ink darker while leaving the rest of the page alone.

  • High Contrast

    Maximum separation between ink and paper. Best for very washed-out scans.

  • Clean Scan

    Removes uneven grey shading and speckles from photocopies and phone scans.

  • Black & White

    Adaptive threshold to pure black on white. Smallest files, no grey at all.

  • Brighten

    Lifts mid-tones and whitens dull paper while keeping the ink solid.

  • Sharpen

    Firms up soft edges only. Tone, paper and colour are left as they are.

  • Fix blurry

    Sharpens soft edges at a chosen blur size, with contrast and darker ink for readability.

  • Cleanup

    Whitens paper, flattens shadows and removes specks. Ink is never touched.

  • Custom

    Exactly the slider values you set, with no preset behaviour.

  • Grayscale (colour only)

    Converts colour to grey and changes nothing else.

  • Grayscale

    Neutral grey output with moderate darkening. Useful for mono printers.

Manual controls

Tucked under Advanced settings, because the tool has to work without them. Auto Print Enhance overrides the sliders with values measured from each page; pick any other mode to drive them yourself.

Text Darkness
Moves the black point and the gamma of the tone curve. This is the control that turns grey ink into black ink, and the first one to raise when a document still prints faint.
Contrast
Controls the steepness of the S-curve between black and white. Raise it when the mid-tones look muddy; lower it if shading and photographs are collapsing into blocks.
Brightness
Lightens or darkens the mid-tones without moving pure black or pure white, so it cannot clip the ink or the paper. On its own it will not rescue a faint scan; it is a fine-tuning control to use after contrast.
Background
How firmly the paper is pushed towards white, using a locally estimated paper level rather than one global value. High settings clean grey scans; very high settings can take faint pencil with them.
Sharpness
An unsharp mask applied after the tone curve, restoring edges softened by scanner optics and JPEG compression. Kept mild by default — heavy sharpening produces halos.
Noise Reduction
A median filter restricted to the paper side of the histogram, so speckle and dust are removed without rounding the corners of small text.
Keep colour
Genuinely saturated content — signatures, stamps, logos, highlighted rows — keeps its hue and is darkened more gently than neutral ink.
Preserve real text
Pages made only of text and vector graphics are darkened by rewriting their colour instructions rather than being turned into images, so text stays selectable, searchable and sharp at any zoom. A page that contains any picture, including a logo, is enhanced as an image.
Thicken thin text
Outlines glyphs on text pages with a hairline stroke. The only lever that helps when the text is already pure black but the font is too thin to print solidly.

What it deliberately does not do

  • The tools here do not run OCR. Real text on digital pages is kept, but scanned pages become images and an existing OCR layer on a scan is not carried over. Text recognition is its own tool: OCR a scanned PDF.
  • No deskewing, cropping or rotation. Page geometry is left exactly as it was.
  • No merging, splitting or page reordering.
  • No editing of text content. Only how it is coloured changes.
  • No accounts, no email, no signup, no watermark on the output.

Start with your job