Compress PDF

Compress PDF shrinks large PDFs, especially scanned documents and photo-heavy files, so they fit email limits and upload portals. It works by re-rendering each page as a JPEG image at the quality and resolution you choose, using Low, Medium or High presets, and then rebuilding the PDF from those images. That approach can cut a bloated scan down dramatically, but it also means the text becomes part of the picture and can no longer be selected or searched. This guide explains when that trade-off is worth it, when it is not, and how to get the smallest readable file. Everything happens in your browser, so your documents are never uploaded.

How to use the Compress PDF

1. 1 Add your PDFDrop a PDF onto the tool or click to choose it. The file is read inside your browser and its current size is shown.
2. 2 Pick a presetChoose Low, Medium or High. Low gives the smallest file with the softest detail, High keeps the most detail with less saving, and Medium sits in between.
3. 3 Compress the fileStart compression. Each page is drawn as an image at your chosen setting and saved as a JPEG, then the pages are rebuilt into a new PDF on your device.
4. 4 Compare before and afterThe tool shows the original size, the new size and the difference. If the result would be larger than the original, it warns you, and you should keep your original file.
5. 5 Check readability and downloadOpen the compressed PDF and zoom in on the smallest text, such as figures on a statement. If it is still clear, download it. If not, try the next preset up.

How this PDF compressor works

PDFs get large for different reasons. A scanned document is really a stack of photographs, often saved at a high resolution with little compression, so a ten-page scan from an office copier or a phone app can easily run to many megabytes. A digital document exported from Word or accounting software, on the other hand, is mostly text and vector shapes, which take up very little space.

This tool treats every page the same way. It draws the page at a set resolution, saves the result as a JPEG at a set quality, and places that image on a new page of the same size. For scans, this replaces an oversized, poorly compressed image with a right-sized, efficiently compressed one, which is where the big savings come from. The Low, Medium and High presets simply choose different combinations of resolution and JPEG quality.

All of this runs in your browser using your own device. Nothing is uploaded, which is important when the PDF is a signed contract, a set of payslips, a bank statement or a scan of your passport.

The honest trade-off: text becomes an image

Because each page is rebuilt as a picture, anything that was real text in the original becomes pixels in the compressed version. You can still read it, but you cannot select it, copy it, or find it with a search. Screen readers cannot read it either, which matters if the document needs to be accessible. Clickable links stop working, fillable form fields stop being fillable, and any digital signature is no longer valid, because the file has been rebuilt.

For a scan this costs you nothing: the text was already an image. For a digital document it is a real loss, and it often does not even save much space, because text-based PDFs are already small. In some cases the rasterised version is actually larger than the original, which is why the tool warns you when that happens.

• Good fit: scanned letters, receipts, signed paper forms, photographed documents, image-heavy brochures and photo reports.
• Poor fit: invoices, contracts and reports exported from software, where the text is real and the file is probably small already.
• Avoid entirely: documents that must stay searchable or accessible, fillable forms, and digitally signed PDFs.

Compress a PDF for email

The most common reason to compress a PDF is an email that will not send. Many email services cap attachments at around 20 to 25 MB per message, and the limit applies to the encoded size: attachments grow by roughly a third when they are prepared for sending. A 19 MB PDF can therefore fail against a 25 MB limit. The receiving organisation may also have a lower limit than your own provider, and you will not always know what it is.

A comfortable target is well under 10 MB for anything you are emailing to someone outside your organisation. For a scanned document, the Medium preset usually gets there while keeping text easy to read. If you are sending several documents, compress each one and check the total. If a file still will not fit, split it into parts with our Split PDF tool and send them as separate messages.

Compressing for upload portals and applications

Online forms for tax, company filings, visa and immigration applications, university admissions, job applications and insurance claims often set a maximum size per file, and some also ask for PDF only. These limits vary between services and change over time, so always check the figure stated on the upload page itself rather than relying on a number you read elsewhere.

Readability matters more than size here. A caseworker who cannot read the figures on a scanned bank statement or the number on an ID document may reject the file or ask you to resubmit, which can add delay. Compress just enough to get under the limit: start with High, check the result, and only drop to Medium or Low if you still need to. Zoom in to 100 per cent or more on the smallest text before you upload.

Choosing the right preset

There is no single best setting, because the right choice depends on what the document contains and where it is going. As a rule of thumb, choose the highest preset that gets you under the size you need.

• High: scans with small print, such as bank statements, payslips, tables of figures or ID documents, and anything that might be printed.
• Medium: everyday scanned letters, receipts and forms that need to be emailed or uploaded comfortably.
• Low: large photo-heavy files where you only need a rough on-screen copy, such as a preview of a brochure or a site photo report.

When to use a different approach

If your PDF is a digital document and it is still too large, the cause is usually large embedded images or fonts, not the text. The best fix is to go back to the source: export again from Word, Excel or your design software with a smaller image setting, or choose a reduced-size PDF option if the software offers one. That keeps the text real and searchable.

Desktop tools such as Ghostscript can also recompress the images inside a PDF while leaving the text as text, which suits digital documents better than rasterising. The example below shows the command. For scans you have not made yet, set your scanner or phone app to a sensible resolution, around 200 to 300 dpi for documents, and colour only where colour matters, since greyscale scans are much smaller. Getting the scan right at the start beats compressing afterwards.

Examples you can copy

Bank statements, payslips, ID scans    -> High
Scanned letters and receipts to email  -> Medium
Photo-heavy brochure, preview only     -> Low
Digital invoice or contract (real text) -> Do not rasterise; re-export instead

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile=smaller.pdf original.pdf

qpdf --object-streams=generate --compress-streams=y original.pdf tidied.pdf

1. Compare the before and after sizes in the tool
2. Keep the original if the result is larger
3. Zoom in on the smallest text and numbers
4. Check the page count matches the original
5. Confirm the size is under the recipient's limit

Common mistakes to avoid

Frequently asked questions