How to Compress a PDF

Why PDFs Get Large

PDF files balloon in size for a few common reasons:

• High-resolution images: Photos and scans embedded at full camera resolution are usually the single largest contributor.
• Embedded fonts: Documents that embed complete font files carry more data than needed.
• Scanned pages: Scans are images themselves, so a 50-page scan is essentially 50 large images.
• Unused objects: Older files often contain duplicate or obsolete data left behind by the software that created them.

Large PDFs are hard to email (most providers cap attachments around 25 MB), slow to upload, and waste storage. Compressing fixes all of that.

How PDF Compression Works

Compression reduces size through three main techniques:

• Image optimization: Embedded images are re-encoded and, when appropriate, downscaled. This is where most of the size savings come from.
• Content stream compression: The internal instructions that describe text, colors, and shapes are compressed with standard algorithms, which does not affect what you see.
• Cleanup: Redundant metadata and unused objects are removed without changing the visible document.

Because text and vector graphics stay sharp, a text-heavy PDF can often be reduced by 70–90% with no visible difference.

How to Compress a PDF in 4 Steps

1. Open the compressor. Visit pdf.openservicetools.com and select the Compressor tab.
2. Add your file. Drag and drop a PDF onto the upload area, or click to browse. Files up to 200 MB are supported.
3. Choose a compression level. Use a preset (small, medium, large) or enter a target size in KB or MB. Lower levels give smaller files with more aggressive image re-encoding.
4. Download the result. Processing happens in your browser. When it finishes, download the compressed copy. Your original is never modified.

Which Compression Level Should You Use?

• For email and web upload: A small or medium level is usually fine. Screen viewing does not need full-resolution images.
• For printing: Choose a lighter setting so embedded images keep enough detail to look good on paper.
• For archiving: Balance size and quality based on how often you will need to read or reprint the document.

A practical starting point: if you need to send a document by email, target 5–10 MB regardless of the original size.

Privacy When Compressing PDFs Online

Documents often contain sensitive information, so privacy matters. With our tool:

• Client-side processing: Compression runs in your browser, so the file is not uploaded to a server.
• No account needed: You can compress files without registering or providing personal details.
• Automatic deletion: If server-side steps are ever required, files are deleted immediately after processing.
• Encrypted connections: All transfers use HTTPS.

Common Problems and Solutions

The compressed PDF looks blurry

Switch to a lighter compression setting. The "medium" or "large" presets keep more image detail for documents that will be read closely or printed.

The file did not shrink much

Text-only PDFs with few images have limited compression headroom. Try a smaller target size, or re-create the PDF from a lower-resolution source if that is an option.

I need to combine multiple PDFs afterward

Compress each file first, then use the PDF merger to combine them. Merging already-compressed files keeps the final document small.

Frequently Asked Questions