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PDF Resolution Reducer

Adjust image pixel targets while keeping JPEG quality separate; both steps can lose detail.

Processed locally in your browser. Your file is not uploaded to any server. How this works

  1. 01Add your file
  2. 02PDF Resolution Reducer
  3. 03Download

Runs in your browser · nothing uploaded

About PDF resolution reducer

Resolution in a PDF is a relationship, not a property of the image alone: pixel dimensions are divided by the physical size at which an image is placed. A 3000-pixel-wide photograph placed across ten inches has 300 pixels per inch, while the same image placed across two inches has 1500. Whether those extra pixels matter depends on the intended reproduction size, zoom and fine detail; they are not automatically invisible waste. This tool derives a pixel target from recoverable image placement and the selected DPI. Not every placement can be measured, particularly in more complex content, so some candidate images can be re-encoded without being downsampled. Supported images below the target keep their dimensions but may also undergo JPEG re-encoding. Halving both dimensions leaves about one quarter of the pixels, not a guaranteed quarter of the encoded bytes. Each replacement is kept only if smaller, and accepted downsampling and JPEG changes are lossy even at high quality. The PDF also undergoes object-stream rewriting and optional limited metadata cleanup targeting eight standard Info keys and the catalog XMP reference; other metadata and detached XMP bytes may remain. A smaller complete candidate is returned, otherwise the original bytes, images and metadata are retained. Compare one setting at a time, inspect small text at the intended size, and keep the original rather than assuming the target guarantees every image's resolution or appearance.

How to PDF resolution reducer

  1. 01

    Load the document

    Add one unencrypted PDF, up to 250 MB and 5,000 pages. Scans and camera photographs may offer savings when their image streams can be decoded and placements measured.

  2. 02

    Choose a resolution honestly

    Choose for the intended viewing or print size. Lower targets can soften fine detail; higher targets do not add detail to low-resolution sources or guarantee print suitability.

  3. 03

    Keep quality high

    Start at the initial 85% JPEG setting and change one control at a time. High quality is still lossy, and a resolution change does not disable re-encoding below the target.

  4. 04

    Reduce and check

    Read whether the rewrite or original was returned, then inspect detailed images and scanned text. A -compressed.pdf name does not prove downsampling; check the report and keep the original.

What this tool does

  • Calculates image pixel targets from recoverable placement, rather than assuming every image has a known DPI
  • Keeps below-target image dimensions, while still allowing smaller JPEG re-encoded replacements
  • JPEG quality starts at 85% and remains separately adjustable; image encoding is not lossless
  • Can reduce supported images carrying more pixels than needed for the intended size and detail
  • Everything runs locally, with no upload of the source document

Limitations worth knowing

Every PDF tool has constraints. Stating them plainly is more useful than discovering them halfway through your work.

  • Downsampling permanently discards pixels. Zooming further than the new resolution supports will look soft, and the detail cannot be restored.
  • Vector drawing operators are not deliberately downsampled. A vector-heavy file may still change size through structural rewriting or limited metadata cleanup.
  • Text drawing operators and embedded fonts are not deliberately rasterized, but this tool does not validate every rendering detail. Text-only files may still benefit from structural rewriting.
  • Downsampling and JPEG artefacts can impair scanned-text readability and later OCR. Preserve a high-quality original for recognition; this tool does not add or validate an OCR text layer.

How your file is handled

This tool runs entirely inside this browser tab. When you choose a file, your browser reads it from your own disk and hands the bytes to JavaScript running on this page — no network request carries your document anywhere. You can confirm that yourself: open your browser’s developer tools, switch to the Network panel, and run the tool. You will see no upload.

Nothing is stored after the fact. Closing or reloading this tab discards the file, the result and everything derived from them, because none of it ever left your machine. Read how local processing works.

Questions about PDF resolution reducer

How do I know what DPI my images currently are?

Divide an image's pixel width by its placed width in inches, and consider its height as well. An inspector can estimate effective DPI only where placement is recoverable; complex page content may prevent a complete inventory. A high number alone does not mean detail is disposable, especially when the document will be enlarged or printed. Use the intended reproduction size and inspect the result.

Is reducing resolution better than lowering JPEG quality?

Neither is universally better. Downsampling removes pixels and can be useful when supported images carry more detail than the intended viewing size needs. Lower JPEG quality changes how the remaining pixels are encoded and can introduce artefacts without changing dimensions. This page performs both kinds of processing, including re-encoding below the DPI target. Change one setting at a time and judge file size alongside small text and image detail.

Will downsampling blur my scanned text?

It can. Readability depends on source quality, type size, contrast, JPEG artefacts and the size at which the page is viewed or printed, not a universal DPI threshold. Lower targets can lose thin strokes or small characters, while even a high target does not improve a poor scan. Keep the original for OCR and inspect the returned file before relying on its text.

Why did nothing change when I reduced the resolution?

There are several possibilities: images may already be below the target, their placement may be unavailable, the browser may not decode them, or the replacement streams may not be smaller. A whole rewritten PDF that is not smaller is also discarded in favour of the original. Read the candidate counts together with the returned-file result; no size change does not prove that no oversized images exist or that another method could not help.

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