Reduce PDF File Size

Email providers, grant portals, and job application sites routinely cap attachments at a few megabytes. When a PDF is too large, you need to shrink it — ideally without handing the document to an unknown upload service. This guide explains how to reduce PDF file size locally in your browser with the Compress PDF tool, and what honest limits apply.

TL;DR

Open the Compress PDF tool, add your PDF, set a target size (for example under 2MB), and run compression. The tool attempts to reach the target entirely in your browser and tells you plainly if the target is not reachable.

What browser-based compression can do

A PDF can contain several kinds of data that contribute to its size: raster images embedded as JPEG or Flate streams, vector drawings, fonts, and scanned pages. Browser-based compression primarily re-encodes the embedded raster image streams at a lower quality or resolution using pdf-lib, which rewrites the document without the original high-resolution image data.

This approach is effective when the PDF’s bulk comes from large embedded images — which is the common case for scanned documents, photo-heavy reports, and print exports. It is less effective on PDFs that are large because of embedded fonts or complex vector content, because those elements are not image streams the tool can re-encode.

Step-by-step

1. Open the Compress PDF tool at /en/tools/pdf/compress-pdf/.
2. Add your PDF. Select the .pdf file you want to shrink.
3. Set a target size. Enter the size you need the file to fit under (the under-2MB variant targets 2MB by default).
4. Run compression. The tool reads the PDF, re-encodes its image streams, and measures the result against your target.
5. Read the honest result. If the target is reached, download the smaller PDF. If the target is not reachable, the tool tells you the smallest size it could achieve and why.

Honest limits

• A target size is not guaranteed. If a PDF is already efficiently encoded, or its size comes from non-image content, the tool may not be able to reach an aggressive target. The tool reports the actual achievable size rather than silently returning an unchanged file.
• Quality decreases with compression. Re-encoding images at lower quality reduces visible fidelity. For documents with fine text or detailed diagrams, preview the result before relying on it.
• Scanned pages compress well; vector PDFs do not. A scanned form embedded as images has a lot of compressible image data. A vector logo sheet or font-heavy document may barely shrink.
• No OCR and no page removal here. To cut size by removing pages, use Remove PDF Pages instead.

When to use a target size vs. merge first

If you have many separate PDFs and a combined size limit, merge them first with the Merge PDF tool, then compress the single result toward your target. Compressing each file separately and then merging usually produces a larger total because merge re-embeds pages without re-compression.

FAQ

Why can’t the tool reach my target size every time?

Compression re-encodes image data, so the achievable size depends on how much image data the PDF contains and how it was originally encoded. A PDF that is large because of embedded fonts or vector content has little image data to re-encode, so an aggressive target may be unreachable. The tool tells you the real minimum it can achieve.

Will compression damage text searchability?

Re-encoding embedded images does not remove the text layer of a PDF that has one. However, if the PDF is a scan with no text layer (just images of pages), compression reduces image quality but cannot add searchable text — that requires OCR, which is out of scope here.

Is it safe to compress confidential PDFs here?

The PDF is processed entirely in your browser and is not uploaded. As always with sensitive documents, use your judgment and close the tab when done.