Compress PDF

How to compress a PDF

1. Drop the PDF on the box above, or tap it to pick a file from your phone or computer.
2. For a first try, leave Image quality at 60% and Resolution at Medium. These suit most scanned forms, certificates and ID copies.
3. If the portal gives a size limit, type it in Target size (for example 200) or tap one of the 100 KB, 200 KB, 500 KB or 1 MB buttons. The tool then picks the settings for you.
4. Press Compress and download. The new file gets “-compressed” or the target size added to its name, so your original is never overwritten.
5. Open the result and zoom into the smallest text — a roll number, a date, a signature — before you upload it.

What makes a PDF large

A PDF is a container. Typed text is stored as characters plus the font needed to draw them, which takes very little space, so a long report made in Word is usually small. Pictures are what make PDFs heavy. A phone scan of a marksheet is really a photograph of the page, and a modern phone camera captures 12 megapixels or more, in full colour, for every page. Scanner apps and office photocopiers set to 300 or 600 dpi colour do the same, which is how five pages can come to 5–10 MB.

Scanned PDFs and text PDFs

To tell them apart, try selecting a word. If you can highlight and copy text, it is a text PDF — typed in an office program, exported from a website, or a statement downloaded from your bank. If the whole page selects as one picture, or nothing selects at all, it is a scan.

This tool redraws every page as a JPEG image and builds a new PDF from those images. That is exactly what a scan needs: a 4 MB phone scan typically drops to a few hundred KB with no visible change at normal zoom. A text PDF is already compact, and turning its text into pictures can make it bigger rather than smaller. When that happens the tool tells you and does not hand you a larger file. For a text PDF that is still over a limit, removing pages usually helps more than compression.

Greyscale and other fixes at the scanning stage

Most of the size is decided before the file reaches this page. A colour scan stores three colour channels; a greyscale scan of the same page compresses far better and, for a typed certificate or an ID copy, loses nothing that matters. In your phone's document scanner, Google Drive's scan option or Adobe Scan, choose the greyscale or black-and-white filter, crop to the edge of the paper and shoot in good light. Shadows and a grey cast cost kilobytes.

Quality or size: choosing the settings

The two controls do different jobs. Image quality is the JPEG setting: around 60% keeps the edges of letters clean, and below about 35% blocky smudges start to appear around text and stamps. Resolution sets how many pixels each page gets. Small (72 dpi) is fine for reading on a phone, Medium (108 dpi) keeps small print legible on a laptop, and Large (144 dpi) is the one to choose if someone will print the file. Lowering the resolution saves more space than lowering quality, but fine print breaks up sooner, so for a dense form reduce quality first.

With a target size, the tool works through eleven combinations, from Medium resolution at 70% quality down to roughly 30 dpi at 20%, and stops at the first one that fits. You get the sharpest version the limit allows, not simply the smallest file possible. A PDF that is already under the target is left exactly as it is.

Why a PDF won't go below a certain size

Each page needs a certain number of bytes to stay a readable picture of a page, so the floor rises with the page count. A 20-page document squeezed into 100 KB leaves 5 KB a page, which is not enough for print to survive. If the tool reports that the smallest size it reached is still over your limit, you have three options: delete pages the form doesn't need with Remove pages, split the document into parts if the portal accepts more than one upload, or scan again in greyscale.

Typical upload limits

Limits vary from portal to portal and can change from one notification to the next, so always read the instructions for the form you are filling. As a rough guide, many recruitment, scholarship and admission portals ask for documents somewhere between 100 KB and 1 MB per file, certificates such as caste, income or domicile are often limited to a few hundred KB, and photos and signatures have their own, much smaller limits — use Compress image to 20 KB or Passport size photo for those.

Your files stay on your device

Nothing is uploaded. The PDF is opened by pdf.js and rebuilt by pdf-lib inside your browser tab, on your own phone or computer, and the result comes straight back to you as a download. That matters for Aadhaar and PAN copies, bank statements, medical reports and marksheets. Once the page has loaded it keeps working even if you switch off mobile data, and closing the tab clears everything.