How to reduce PDF size for an upload limit (under 2 MB, 500 KB or 200 KB)

How to · Updated 2026-11-10

Turn on Fit an upload limit, pick the size the portal allows, and the PDF is shrunk on your own device. The maths of DPI and page images, with a worked example.

To get a PDF under an upload limit, rebuild its pages at a lower resolution until the file fits, but no lower than you need. The file compressor does this in your browser: switch on Fit an upload limit, choose the size the portal allows, and press Compress. Nothing is uploaded while it works.

What you need

• The PDF. Up to 200 MB on a computer or 50 MB on a phone, because the browser holds the whole file in memory.
• The exact limit. Job, visa, college and exam portals say it on the upload page, often as 200 KB, 500 KB, 1 MB or 2 MB.
• A copy of the original. The smallest settings turn pages into pictures, so keep the first file in case you need to select or search its text later.

Step by step

A PDF is mostly big for one reason: pictures. A scanned page is a photo of paper, and a photo’s size depends on how many pixels it has. The number of pixels comes from the page size and the DPI (dots per inch):

pixels across = page width in inches × DPI pixels down = page height in inches × DPI

PDF pages are measured in points, and 72 points make an inch, so width in inches = points ÷ 72. An A4 page is about 595 × 842 points.

The key idea is that pixel count grows with the square of the DPI. Dropping from 150 to 100 DPI keeps (100 ÷ 150)² ≈ 0.44 of the pixels, so each page image holds less than half as much to store. That is why a small change of DPI makes a large change in size.

With the compressor:

1. Choose your PDF, or drop it onto the box. The tool shows its name, size and the type it detected.
2. Turn on the Fit an upload limit switch.
3. Tap a size chip (100 KB, 200 KB, 500 KB, 1 MB or 2 MB), or type any number of kilobytes in Or exactly (10 KB or more).
4. Press Compress. The tool first tries a light repack that keeps the text selectable. If that is still too big, it rebuilds the pages as images, starting at 150 DPI and stepping down.
5. Read the result: the Before and After sizes and how much smaller the file got. Then press Download.
6. If the file cannot fit without a visible drop in quality, the tool stops at the best clean version and says so. You then choose: keep that version, or press Go below anyway to accept softer pages.

Without the switch, you pick a level yourself: Light (text, links and form fields stay), Recommended (pages as images at 150 DPI) or Smallest (pages as images at 100 DPI).

A worked example

Maya scanned a 6-page set of certificates on her phone. The PDF is 4.8 MB, and the college portal allows 2 MB.

First, what does 2 MB mean in bytes? Computers count 1 KB as 1,024 bytes and 1 MB as 1,024 KB, so:

• 2 MB = 2 × 1,024 = 2,048 KB = 2,097,152 bytes.

Spread across 6 pages, each page can use about 2,048 ÷ 6 ≈ 341 KB.

Now the page pictures. For an A4 page:

• At 150 DPI: 595 × 150 ÷ 72 ≈ 1,240 pixels across and 842 × 150 ÷ 72 ≈ 1,754 down, about 2.17 million pixels.
• At 100 DPI: about 826 × 1,169, roughly 0.97 million pixels.

So the 100 DPI page has about 44% of the pixels of the 150 DPI page.

Maya taps 2 MB and presses Compress. Suppose the result reads 1.62 MB. The saving shown is:

• (1 − 1.62 ÷ 4.8) × 100 ≈ 66% smaller.

That fits with room to spare, and she uploads it. Your own file will give different numbers, because a page of dense handwriting packs less well than a page of clean type.

Check your answer

• Look at the After figure, not the file name. It must be at or below the portal’s number. Some portals count 1 MB as 1,000,000 bytes, so if a file sits right on the edge, aim a little lower.
• Zoom in on the smallest text. Signatures, dates and roll numbers must still be readable at 100% zoom. If they are blurry, try again without Go below anyway.
• Count the pages. The number of pages should match the original.
• Rough size check. Six pages under 2 MB is about 340 KB a page, which is plenty for a clear scan. A 40-page file under 200 KB is only 5 KB a page and will rarely look good.

Questions people ask

Why can I no longer select the text? At Recommended, Smallest or a tight upload limit, each page becomes a picture of itself. Choose Light to keep text, links and fill-in fields, if the limit allows.

What if it still will not fit? Split the file and upload the parts, if the portal allows more than one file. The organise PDF tool splits, reorders and removes pages, so you can also drop a blank back page or two.

How do I make a smaller scan in the first place? Photograph each page in good light and turn the photos into one PDF with scan to PDF. For a single picture rather than a PDF, the image resizer can shrink it under a limit too.