pdf24 compress PDF: make a PDF smaller, free and private

Yes. pdf24 compress PDF on pdf24tools costs nothing, needs no account and adds no watermark. There is no daily cap, because the work runs on your own device and uses no server time. You can compress one file or a whole batch, as often as you like, and keep every result.

No. pdf24 compress PDF reads the file from your disk and processes it in memory with pdf.js and pdf-lib. The result line shows 0 bytes uploaded, and closing the tab removes everything. You can check it yourself: load the page, switch off Wi-Fi, and the compressor still works.

Choose Exact size and type 100, or open the ready-made 100 KB page. The tool tries up to 10 settings until the file fits. Our 5-page scan of 2.46 MB reached 82 KB. A long scan may not fit 100 KB while staying readable; then split it or remove pages first.

Usually, yes. With pdf24 compress PDF a 4-page scan of 8.07 MB became 770 KB on Recommended and 337 KB on Strong in our test. For a fixed 1 MB limit choose Exact size and type 1000, so the tool stops at the best quality that still fits instead of going smaller than needed.

Only when the lossless pass wins, which happens with typed documents that contain few or no pictures. When pages are redrawn as JPEG the text becomes part of the picture and can no longer be selected or searched. Run OCR PDF on the compressed file if you need searchable text again.

The message appears when neither the lossless re-save nor any redrawn version is smaller than your original. That is typical for PDFs made by a careful export from Word or LaTeX with no photos. The tool then returns the original unchanged instead of a heavier or blurrier copy.

The Recommended level of pdf24 compress PDF suits almost everything read on a screen: email, chat and portal uploads. Choose Light when the file will be printed or contains small print and thin lines. Choose Strong, or an exact size, only when a hard limit forces you to go as small as possible.

Yes. Select or drop as many PDFs as you need; they are compressed one after another with the same level and returned in one ZIP file. Each output keeps its name with -compressed added, and the status line lists the saving for every file so you can spot one that did not shrink.

Yes. Open pdf24 compress PDF in Safari or Chrome on iPhone or iPad, tap Choose PDF files and pick the document from the Files app or iCloud Drive. Save the result back to Files or share it straight to Mail. Very long scans take more time on a phone than on a computer.

Yes, in Chrome, Edge, Firefox or Samsung Internet. Pick the PDF from Downloads, Google Drive or a messenger folder, compress it and save the result to Downloads. If the tab reloads during a very long scan, the phone ran out of memory: split the file and compress the parts.

Yes, once the page has loaded. All the code that reads, redraws and saves the pages is downloaded with the page and runs locally, so the tool keeps working after you disconnect. The next visit is faster too, because the browser caches the PDF engine.

There is no fixed limit set by us. The practical limit is your device's memory, which is smaller on a phone than on a laptop. Our largest test file, 8.07 MB with 4 pages, finished on every level without trouble. Very large files are best split into parts first and compressed one part at a time.

No. A file from pdf24 compress PDF contains only your pages, with nothing added on top or in the margins. The file's producer field shows the library that wrote it, as with any PDF program, but nothing is visible on the pages and no logo or link is inserted.

Yes, any change to a signed PDF breaks the signature, because the signature protects the exact bytes of the file. Compress the document first and sign it afterwards. If you received a signed file, keep the original for proof and send a compressed copy only for reading.

When pages are redrawn as pictures, links, form fields and comments are lost, because only the visible page is kept. The lossless pass keeps them. If interactive parts matter, use Light on a file with few pictures and check the result, or keep the original for forms.

Seconds for most files. On a laptop our 2.46 MB scan took 2.5 seconds on Recommended and the 8.07 MB scan about 11 seconds. Exact size needs several attempts, so the 200 KB target took 28 seconds. Time grows with page count, and a phone is slower than a computer.

Yes, photo PDFs shrink the most with pdf24 compress PDF, because phone pictures are much larger than a page needs. Recommended redraws each page at 90 DPI, which looks sharp on a phone screen. To build a small PDF straight from photos, the JPG to PDF tool also has an under-size option.

Strong and low Exact size targets lower the resolution to about 65 DPI or less, which softens small print. Run the original again on Light or Recommended, or raise the target size. A higher target lets the tool stop at an earlier, sharper step of its 10-step ladder, so allow as many kilobytes as the form accepts.

Not directly. An encrypted PDF must be opened with its password first. Remove the protection with Unlock PDF, compress the unlocked copy, and lock it again with Lock PDF if the recipient needs the password. Only do this with files you are allowed to change.

It works in current versions of Chrome, Edge, Firefox and Safari on Windows, macOS, Linux, ChromeOS, Android and iOS. Internet Explorer is not supported. If the Compress PDF button stays grey, reload the page so the PDF engine can finish loading.

No. pdf24tools is an independent website and is not affiliated with PDF24 or Geek Software GmbH. Our compressor is our own build using the open-source pdf.js and pdf-lib libraries, running entirely in your browser. The name only reflects what many people type when they look for a free PDF compressor.

You can, but compressing an already compressed file twice adds blur for little gain. It is better to run the original once more with a stronger level or a smaller Exact size. The tool always starts from the bytes you give it, so the original is the best starting point.

No. Every page keeps its original dimensions, such as A4 or US Letter, and its orientation. Only the resolution of the picture drawn on the page changes. To change the paper format itself, for example from A3 to A4, use the Change PDF page size tool.