Compress PDF
Reduce your PDF file size. Choose a preset compression level, or input a custom target size (like 200KB).
Drag & Drop a PDF file here
or click to browse from your device
PDF file sizes can grow unexpectedly large, especially when documents contain high-resolution images, embedded fonts, or were exported from design software. A 50MB PDF is difficult to attach to an email, too slow to load on a mobile connection, and takes up unnecessary storage space. PDFLocal's Compress PDF tool reduces your PDF's file size directly in your browser, using client-side image resampling and content stream optimization techniques — with no file uploads and no waiting.
The compression process works by analyzing each image embedded within the PDF and re-encoding them at a lower resolution or quality level appropriate for on-screen reading rather than professional printing. Vector graphics and text content are preserved at full quality since they are resolution-independent and do not contribute significantly to file size. The result is a smaller file that looks virtually identical on screen but occupies significantly less disk space.
Steps to Compress a PDF Offline
- Upload: Drop your PDF into the compression zone. The tool immediately displays the original file size.
- Select Compression Level: Choose between Low (minimal quality reduction), Medium (balanced), or High (maximum size reduction) compression presets.
- Compress & Compare: Click Compress. The tool shows you the before and after file sizes so you can see exactly how much space was saved.
- Download: Save the compressed PDF to your device with one click.
Frequently Asked Questions
How much can PDFLocal reduce my PDF file size?
The amount of size reduction depends heavily on the content of your PDF. Image-heavy PDFs (such as scanned documents, photo portfolios, or design mockups) typically see the most dramatic reductions — often 60% to 85% size reduction at medium compression settings. Text-heavy PDFs with minimal images (such as legal contracts or word-processed reports) see smaller reductions, typically 10% to 30%, since most of the file size is already taken up by efficient text encoding rather than images. The compression preview feature shows you the exact reduction achieved before you download, so you can always try different settings and compare results.
Will compressing a PDF reduce the quality of text and fonts?
No. Text content and vector graphics (including scalable shapes, diagrams, and line art) are not affected by the compression process. Only raster (bitmap) images embedded within the PDF are recompressed. The text in your compressed PDF will remain crisp, fully searchable, and selectable at any zoom level. Font rendering quality is completely unchanged. The only visible quality difference, if any, will be in photographs or detailed bitmap images — and even at medium compression, most users cannot distinguish the difference when reading on screen.
Can I compress a scanned PDF without losing readability?
Yes, but the results depend on the original scan quality and the compression level you choose. A scanned PDF is essentially a collection of photographic images of each page, so compression will re-encode those images at a lower quality. For scans of text documents (receipts, contracts, handwritten notes), the Medium compression setting typically maintains excellent readability while reducing file size by 50-70%. If the original scan was at a very high DPI (600 DPI or above, common with photo scanners), significant compression can be applied with no visible readability loss because the text was over-sampled to begin with. We recommend using the preview feature to check readability before downloading when working with important scanned documents.
Why is my compressed PDF larger than the original?
This can occasionally happen with PDFs that have already been heavily optimized or that contain very few images. When a PDF is processed through the compression pipeline, the tool adds some minimal structural overhead (updated cross-reference tables, version headers). If your original file was already tightly compressed and contains mostly vector graphics or text, the overhead can sometimes exceed the savings from image recompression, resulting in a marginally larger output. In these cases, simply use the original file — PDFLocal's preview shows you the sizes before and after, allowing you to make an informed decision.
Is there a file size limit for the compression tool?
There is no enforced file size limit. However, because the compression process runs entirely in your browser's memory, very large PDFs (over 200MB) may take 30-60 seconds to process on a typical laptop. During this time, the browser tab will be fully occupied with the compression computation. For very large files, we recommend keeping the browser tab active and in focus during compression. If the tab is backgrounded or the screen locks, some mobile browsers may pause the processing to save battery — so keep the screen active until the download begins.
Does the compressed PDF retain digital signatures?
This depends on the type of signature. Visual signature images (a picture of a handwritten signature placed on the document) are raster images and will be slightly recompressed along with other images in the PDF. This does not affect their visual appearance at normal zoom levels. Cryptographic digital signatures (the kind used for legally binding e-signatures, typically shown as a blue verification banner in PDF readers) will be invalidated by the compression process, because compression modifies the binary content of the file, which breaks the cryptographic hash that validates the signature. If your PDF has cryptographic digital signatures that need to remain valid, do not use compression after signing.
How do I compress a PDF to under 1MB for email?
Start with the High compression preset, which is specifically tuned to produce the smallest possible file while maintaining readability. If the result is still over 1MB, there are a few additional strategies: First, check if the PDF contains unnecessary pages that could be removed using the Split or Edit PDF tools. Second, if the PDF was created from a design application (InDesign, Illustrator), re-export it at a lower DPI setting from the original application before running it through PDFLocal. Third, for scanned documents, re-scan at 150 DPI (sufficient for on-screen reading) rather than 300+ DPI, which is only needed for print quality.
Can I compress multiple PDFs at once?
Currently, PDFLocal processes one PDF at a time in the compression tool. For batch compression of multiple files, you can process them one by one using the tool, or alternatively merge all your PDFs first using the Merge PDF tool, compress the merged file, and then split it back if needed. A batch processing mode for the compression tool is on our feature roadmap. In practice, most users find the individual processing workflow fast enough — a 20MB scanned PDF typically compresses in under 10 seconds on a modern laptop.