How to Compress a PDF Under 1 MB for an Upload Form
An application form says 'maximum file size 1 MB' and your scanned passport and certificates come to 4.7 MB. A one-megabyte limit is tight, but most documents can get under it if you work in the right order: start with the gentlest change and stop as soon as the file fits.
Find out what makes your PDF heavy
Check the size first (right-click the file and choose Properties on Windows, or Get Info on a Mac). Then think about what is inside. Pages typed in Word or exported from a website are mostly text and take up very little room. Scanned pages and phone photos are pictures of paper, and pictures are where almost all of the size lives.
A good rule of thumb: if your PDF came from a scanner or a camera, compression will make a big difference. If it is a ten-page typed report that is already 900 KB, there is not much image data to squeeze, and removing pages will help more than compressing.
Step 1: compress at the recommended level
Open Compress PDF and add the file. Leave the level on Recommended, which keeps images at 150 dpi: sharp on screen and fine to print on an office printer. Press Compress PDF and look at the new size shown on the result screen.
For many scanned documents of two to five pages, this alone lands under 1 MB. Before you upload, open the result and zoom in on the smallest print, such as a passport number or the date on a certificate, to make sure it is still easy to read.
Step 2: use the strongest level if you are still over
If the file is still above the limit, go back to the original, not the compressed copy, and choose Extreme. It brings images down to 72 dpi, the lowest setting, which is meant for documents that will only be read on screen. Compressing an already compressed file again saves very little and makes text in scans fuzzy, so always start each attempt from the original.
Check readability again at 100% zoom. Upload systems are read by people: a file that fits but cannot be read gets your application sent back.
Step 3: switch colour scans to black and white
A colour scan of a black-and-white page stores three colour channels for paper that is mostly white. Converting it with PDF to Black and White, then compressing, often cuts the size noticeably while keeping stamps and signatures visible as dark grey.
Do not do this for documents where colour carries meaning, such as a coloured photo ID that the form asks to see in colour, or a chart where lines are told apart by colour.
Step 4: remove pages the form does not need
Many bundles carry pages nobody asked for: blank backs of single-sided documents, cover sheets, the terms and conditions page of a bank statement. Delete them with Delete PDF Pages, then compress what is left. Each scanned page you remove takes its full share of the size with it.
If the form lets you upload more than one file, split the bundle instead: Split PDF can produce, say, the passport pages in one file and the certificates in another, each comfortably under 1 MB.
Step 5: if nothing works, scan it again smaller
A document scanned at 600 dpi in colour is far bigger than the form will ever need. Rescanning at 150 to 200 dpi, in greyscale, produces a file a fraction of the size before any compression. On a phone, a clear photo in good light, cropped to the page, works better than a dark, wide shot.
If you are combining several photos into one PDF, shrink the photos first with Compress Image, then build the PDF. Smaller pictures going in means a smaller PDF coming out.
A quick checklist before you upload
The file is under the limit shown on the form, not just close to it, since some portals count 1 MB as 1,000,000 bytes rather than 1,048,576. Every page the form asked for is there. The smallest text is readable at normal zoom. The file name says what it is, for example Passport-Ahmed-Khan.pdf, so the person reviewing it does not have to guess.