Compress PDF

What actually makes a PDF large

When someone needs to compress a PDF, the file is nearly always large for one reason: images. A page of text, even a long one, costs a few kilobytes. A single photograph or a scanned page can cost several megabytes on its own. So a fifty-page report full of text might be under a megabyte, while a five-page scanned contract is thirty — and the way to reduce PDF file size is almost entirely a question of what to do about the pictures.

This tool recompresses those images and leaves everything else alone. Each embedded JPEG is decoded, optionally scaled down, and re-encoded at a lower quality, then written back into the document in place. The text, the fonts, the vector graphics and the internal structure are copied across untouched. The result is a smaller PDF whose text you can still select, search, copy and read aloud with a screen reader.

The trade-off other compressors do not mention

It is worth knowing how the impressive numbers advertised by most online PDF compressor tools are produced. The quickest way to make a PDF smaller — dramatically smaller — is to render every page as a picture and throw away everything underneath — the text layer included. The file shrinks enormously and looks identical at first glance, which is exactly why the approach is popular. What you lose only becomes obvious later: you can no longer select or copy a sentence, search no longer finds anything, the document becomes unreadable to screen readers, and any future editing is impossible because there is nothing left to edit.

That is a reasonable trade for a flyer and a bad one for a contract, and it should be your decision rather than a side effect. This compressor never makes it for you. If a document is mostly text, there is little to recompress and it will say so plainly instead of rasterising the pages to manufacture a percentage.

Choosing a compression level

Light keeps every image at its original dimensions and only re-encodes it, which typically trims a modest amount with no visible change. Balanced scales images to three quarters of their size first and suits most documents — it is the right starting point when you want to make a PDF smaller for email. Strong halves the image dimensions and is where a large scan becomes genuinely portable, at the cost of visible softening if you zoom in. Turning off image recompression entirely gives a lossless pass that only repacks the file structure; the saving is small, but nothing in the document changes at all.

Whichever you choose, the result panel reports the real before and after sizes, the percentage saved, and how many images were recompressed, skipped for being already small, or left alone because they are in a format that cannot be rewritten safely. If compression would not actually help, it tells you that rather than handing back a file of the same size with a success message.

Everything runs on your own device. The PDF is never uploaded, there is no queue and no retention policy to read, and once this page has loaded it keeps working offline. Your original file is never modified — you always get a new document back.