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Grayscale PDF Converter

Convert a bounded PDF to a local grayscale raster PDF with an explicit per-pixel transform.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Choose one local PDF up to 25 MB.
  2. 2.Select Convert to grayscale and wait while every bounded page is rendered locally.
  3. 3.Review the raster PDF and download it when flattened pages meet your needs.

About Grayscale PDF Converter

Grayscale PDF Converter makes a new grayscale PDF from a local document without uploading the source file. It renders each page in your browser, calculates a gray value for every visible pixel, writes a PNG page image, and assembles those images into a new PDF. This visual approach covers ordinary color content consistently because the browser's PDF renderer resolves the original page before the grayscale calculation begins.

The gray value uses explicit pixel arithmetic: 0.2126 times red plus 0.7152 times green plus 0.0722 times blue, rounded to the nearest 8-bit value. The result is assigned to red, green, and blue for every rendered pixel. This avoids relying on the CSS canvas filter property, which is not a dependable default path in Safari. It also makes the behavior testable for black, white, gray, and the primary colors. The tool processes the displayed raster pixels, not a loosely defined set of PDF color operators.

The tradeoff is important. The output is a raster PDF, not a vector-preserving recolor of the original file. Selectable text, live links, form fields, annotations, vector paths, layers, original image encodings, accessibility structure, metadata, and the original compression are not preserved by this version. The resulting file can be larger than the source. The page dimensions are preserved, but the visual detail is rendered at a fixed 1.5 scale before being placed back on a page of the original size.

Before any output page canvas is allocated, the tool checks every PDF page at that scale. It accepts a file up to 25 MB and limits the job to 40 pages, 12,000 pixels on either side of one rendered page, 40 megapixels per page, and 100 megapixels across the document. Those limits keep one browser tab from trying to hold an unbounded image buffer. Starting another conversion cancels the previous job, and canvases, PDF worker tasks, and temporary download URLs are released when they are no longer needed.

Use this converter for a quick visual monochrome copy, print preview, upload requirement, or reference document when flattened pages are acceptable. Use a professional PDF editor when you need to preserve interactive text, PDF/A compliance, accessibility tags, vector graphics, signatures, print color management, or controlled compression. Keep your source file and inspect the grayscale output before sharing it. Password-protected, malformed, signed, or unusually complex PDFs may fail; this tool does not bypass passwords, validate signatures, or claim archival or legal conformance.

Methodology & sources

Validate and load one bounded PDF with PDF.js, preflight every 1.5-scale page against page, dimension, per-page, and aggregate pixel budgets, render each page on an opaque canvas, replace RGB channels with round(0.2126R + 0.7152G + 0.0722B), encode a PNG, place it at the original page dimensions in a new pdf-lib document, reopen the output to verify the page count, and release all temporary resources on completion or cancellation.

Frequently asked questions

Does the output preserve selectable text and links?
No. This version rebuilds each page as a grayscale raster image inside a PDF.
Which grayscale method is used?
Each pixel uses rounded 0.2126 red plus 0.7152 green plus 0.0722 blue.
Why can the grayscale PDF be larger?
Rendered PNG page images can use more bytes than the source PDF's original fonts, vectors, and image compression.
Is the PDF uploaded?
No. PDF rendering, pixel conversion, PNG encoding, and PDF assembly stay in the current browser tab.

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