How to Compress a PDF Without Losing Its Bookmarks

Updated 2026-11-04

Compressing a PDF usually means rewriting it, and a rewrite can drop things that are not page content - above all the bookmark outline in the sidebar. A 300-page manual that shrinks nicely but loses its table of contents is not much use.

This guide compresses a PDF in your browser with two engines, keeps the text selectable when you want it to, and checks that the bookmarks made it into the result. Files are processed locally and never uploaded.

Use the tool: Compress PDF Online

Compress step by step

Open your PDF with "Open PDF", then choose "Compress PDF" from the "Tools" menu (on the Compress PDF page the options open by themselves once the file has loaded)
Pick the engine: "Smart (keeps text)" is the default and the right choice for most files; "Rasterize (max for scans)" is for image-only scans where you want the smallest possible file
Pick a quality preset: "High Quality" (300dpi), "Balanced" (150dpi, the default and recommended) or "Extreme" (72dpi, smallest file)
Click "Start Compression". The first time you use Smart mode, the compression engine (about 10MB) is loaded first
Compare the before and after sizes shown under "Compression complete", then click "Download". If the file did not get smaller you will see "Not reduced - try another engine or preset"

What happens to your bookmarks

When either engine finishes, the tool looks at the result. If the original had bookmarks and the compressed file does not, it copies the original bookmark tree into the result (compression keeps the page count unchanged, so the entries map one to one). If the engine already kept the outline, the file is left exactly as the engine wrote it.

We tried both engines on a small test PDF with a two-level outline: the Smart output kept the full outline, and the Rasterize output ended up with the same bookmarks pointing to the same pages. Results can differ with unusual files, so for an important document open the compressed copy and click a few bookmarks before you delete the original.

Smart or Rasterize?

Smart compression rewrites the document and downsamples images while leaving text and vector graphics untouched, so text stays selectable and searchable. Choose it for most PDFs - reports, papers, ebooks, manuals.

Rasterize renders every page as an image. It gives the highest reduction for pure scans, but the text is no longer selectable - run OCR afterwards if you need searchable text. The bookmarks are still carried over by the check described above.

Start with "Balanced". If the file is still too large, try "Extreme" or the other engine; if the quality is not enough, go back to "High Quality".

Check the result

Open the compressed file with "Open PDF", look at the Bookmarks panel and click a few entries to confirm they jump to the right pages. In Chrome’s built-in viewer, open the sidebar and switch to the outline tab next to the thumbnails.

If the size barely changed, the PDF probably has little to squeeze: text-only PDFs are already small. Try the other engine or a lower preset.

FAQ

Will compression remove my bookmarks?

It should not: after compressing, the tool checks the result and copies the original bookmarks back if they are missing. In our test file with a two-level outline both engines ended with the same bookmarks and pages. For an important document, check the result before deleting the original.

Can I still select and search the text after compressing?

Yes with Smart (keeps text). Rasterize turns every page into an image, so the text can no longer be selected.

Why did my PDF get bigger or barely shrink?

Compression helps most with image-heavy files and scans. A small text-only PDF has little to squeeze, and rebuilding it can even add a little overhead - the tool then tells you "Not reduced - try another engine or preset", and you can simply keep the original.

Is my file uploaded?

No. Both engines run in your browser; Smart compression uses Ghostscript compiled to WebAssembly, running in an isolated worker. The engine itself (about 10MB) is downloaded the first time you use it.