Why is my PDF file so large?

Large PDFs usually contain large images, embedded fonts, or leftovers from earlier edits that are still stored in the file. Lossless compression packs the objects into object streams and drops the ones the document no longer uses; it does not merge duplicate images or subset fonts. Image modes go further by replacing page content with compressed JPEG images.

What is the difference between lossless and lossy compression?

Lossless (object streams) makes the file smaller with no change to content. Lossy (High, Medium, Low) re-renders each page as a JPEG, smaller file but text becomes non-selectable and some visual quality is lost.

Can I compress a password-protected PDF?

Encrypted PDFs cannot be loaded or processed by this tool. Remove the password first using your PDF viewer, then compress.

Does compression affect hyperlinks or bookmarks?

Lossless compression preserves hyperlinks, bookmarks, and form fields. Image-based modes convert pages to images, which removes interactive elements. They also write a new file with no document properties: no title, author, producer, or processing dates.

Yes, completely free. No account, no sign-up, and all processing runs in your browser.

Reduce PDF File Size

Open your PDF and choose a compression level to reduce the file size. Lossless keeps everything identical; lower quality modes shrink the file more aggressively by re-rendering pages as images.

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How it works

If you pick Lossless, pdf-lib rewrites the document using object streams and leaves out objects the document no longer uses, such as leftovers of earlier saves, while preserving text, images, bookmarks, form fields, and the document properties exactly. The High, Medium, and Low modes use pdfjs-dist to render every page onto a Canvas, then export each page as a JPEG that pdf-lib stitches into a smaller replacement PDF. Both strategies finish in seconds for typical documents.

Processing runs in your browser

Whether you pick lossless or an image-based quality mode, the entire reduction happens inside your browser memory. The original file is read locally, the smaller replacement is written locally, and the only data leaving the tab is the download you trigger yourself. You can check this yourself in your browser's DevTools Network tab.

Related operations

To stitch multiple PDFs into one before compressing, try merge PDF. For pulling out a subset of pages, use split PDF. To extract pages as standalone images, see PDF to image.

Frequently asked questions

Why is my PDF file so large?: Large PDFs usually contain large images, embedded fonts, or leftovers from earlier edits that are still stored in the file. Lossless compression packs the objects into object streams and drops the ones the document no longer uses; it does not merge duplicate images or subset fonts. Image modes go further by replacing page content with compressed JPEG images.
What is the difference between lossless and lossy compression?: Lossless (object streams) makes the file smaller with no change to content. Lossy (High, Medium, Low) re-renders each page as a JPEG, smaller file but text becomes non-selectable and some visual quality is lost.
Can I compress a password-protected PDF?: Encrypted PDFs cannot be loaded or processed by this tool. Remove the password first using your PDF viewer, then compress.
Does compression affect hyperlinks or bookmarks?: Lossless compression preserves hyperlinks, bookmarks, and form fields. Image-based modes convert pages to images, which removes interactive elements. They also write a new file with no document properties: no title, author, producer, or processing dates.
Is this tool free?: Yes, completely free. No account, no sign-up, and all processing runs in your browser.

Last reviewed September 30, 2026

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