How to compress a PDF to under 1 MB without uploading it

A job portal wants your certificates as one PDF under 1 MB. Your scan is 4.8 MB. Most guides send you to a website that uploads the file to its server — but you can shrink it without the document ever leaving your phone or laptop.

Why PDFs get so big

Almost all of the weight in a PDF comes from images. A scanned page is a photo of paper, often saved at a high resolution and in full colour. Typed text, by comparison, takes almost no space. That is why a ten-page typed report can be a few hundred KB while two scanned pages are several MB.

• Scans and phone photos of documents — each page is a large image. These compress very well.
• Reports with many photos or charts — the images are the size, not the words.
• Typed documents exported from Word or Google Docs — usually small already, and they shrink the least.

Step by step

1. Open Compress PDF and choose your file. It is processed in your browser, so there is no upload wait, even for large files.
2. Pick a compression level. Balanced works for most documents and keeps text sharp enough to print.
3. Download the compressed file. Your original stays untouched, so you can try again with a different level.
4. Check it before you submit. Open the new PDF, zoom into the smallest text, stamps and signatures, and make sure they are still easy to read.

Still too big? Try these

Compression can only remove so much. If the file is still over the limit, the fix is usually in how the pages were made, not in squeezing harder.

• Split it. Many portals accept several files. Use Split PDF to send the pages in parts, each under the limit.
• Rescan in grayscale. Colour pages carry more data than grayscale ones, and most certificates and forms read perfectly well without colour.
• Lower the scan resolution. 150–200 DPI is plenty for reading on screen and for most printers. 600 DPI is meant for archiving photos, not for forms.
• Rebuild from photos. If your pages are phone photos, compress or resize the photos first, then combine them with Image to PDF.

Mistakes to avoid

• Taking screenshots of each page to make a new PDF. It looks fine on your screen, but small text often turns blurry and the file can end up bigger.
• Compressing the same file again and again. Each round lowers image quality further. Start again from the original instead.
• Not checking the result. A file that is under the limit but unreadable will still be rejected by whoever reads it.

Why it matters where the file is processed

The documents people compress for forms are usually personal — certificates, ID cards, bank statements. Many online compressors upload the file to their server to do the work. A tool that runs in your browser does the same job on your own device, so the document is never handed to anyone else. You can read more in Are online PDF tools safe?.