How to Reduce PDF File Size for Any Upload Limit

To get a PDF under an upload limit, first work out why it is large. In almost every case the cause is scanned pages or photos stored at high resolution. Reduce those images, by rescanning at 150–200 DPI or compressing the photos before you build the PDF, and the file usually shrinks dramatically. Structural optimisation helps less, and splitting the file is the fallback when the portal accepts more than one upload.

This guide puts the fixes in the order that saves the most time.

Why is my PDF so large?

A PDF is a container. Text-only pages are tiny: a 20-page report typed in Word and exported to PDF is often under 500 KB. File size explodes when the container holds images:

• Scanned pages. A scanner or scanning app stores each page as a picture. At 600 DPI in colour, a single A4 page can be several megabytes.
• Phone photos. A modern phone photo is 12 megapixels or more. Ten receipts photographed and placed in a PDF can easily pass 30 MB.
• Embedded fonts and leftovers. Full font files, repeated resources and old editing history add some weight, but rarely as much as images.

A quick test: open the PDF and try to select a word with your cursor. If you can't select text, the pages are images, and image size is your problem.

Step 1: Check the actual limit and format rules

Before changing anything, read the portal's rules carefully. Limits are commonly 1 MB, 2 MB, 5 MB or 10 MB. Some portals limit each file; others limit the total. Some accept several files, which opens up splitting (Step 5). Note whether they insist on colour or accept greyscale. Many government and university portals are fine with greyscale for documents like bank statements.

Step 2: Rescan at a sensible resolution

If you still have the paper, rescanning is the most effective fix. These settings work for nearly every upload portal:

The sizes are rough, because paper texture, stamps and JPEG quality all change the result. But going from 600 DPI colour to 200 DPI greyscale commonly cuts a page by 80–90%. Text at 150–200 DPI is perfectly readable on screen.

Step 3: Compress photos before building the PDF

If your pages started as phone photos, shrink the photos first and build the PDF afterwards:

1. Open each photo in the Image Compressor. Choose JPEG, set quality around 70–80%, and reduce the scale if the photo is far larger than needed. A receipt doesn't need 4,000 pixels across; around 1,200–1,600 is plenty.
2. Check the preview: the text must still be readable.
3. Put the compressed images into a PDF with Image to PDF, choosing A4 or US Letter so pages come out a consistent size.

This often turns a 25 MB PDF into one under 2 MB, with no visible difference at normal zoom.

Step 4: Try a structural optimisation

The PDF Optimizer on ToolMany re-saves your PDF with a leaner internal structure (compressed object streams) and shows you the real file size before and after. It doesn't resample images, so it is most useful for PDFs built from many sources or edited several times. On a pure scan the saving may be small, and occasionally the new file is no smaller. Because it reports the actual numbers, you can see straight away whether it helped.

If you are comfortable with desktop software, these free tools can downsample images inside an existing PDF:

• macOS Preview: File → Export → Quartz Filter → "Reduce File Size". It is aggressive, so check readability afterwards.
• Ghostscript (Windows, macOS, Linux): the command gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -o smaller.pdf input.pdf resamples images to around 150 DPI.
• LibreOffice Draw: open the PDF, then File → Export as PDF with JPEG compression and "Reduce image resolution" ticked. Layout can shift on complex pages, so review it.

Step 5: Split the document if the portal allows several files

When a portal accepts several uploads, splitting is quick and loses no quality. Use Split PDF to extract logical parts, such as pages 1–4 as "Bank statement – March" and pages 5–8 as "Bank statement – April". Name each part clearly so the reviewer knows what they are looking at.

The reverse applies too. If you merged several documents with the Merge PDF tool and the result is too big, it is often easier to compress the individual pieces first and merge again.

What not to do

• Don't screenshot pages. Screenshots look fine on your screen but are often blurry when printed or zoomed, and reviewers may reject them.
• Don't zip the PDF. Most portals don't accept ZIP files, and ZIP barely shrinks a PDF anyway because its contents are already compressed.
• Don't crop out information. Removing a page header or account number to save space can make a document invalid.
• Don't keep re-compressing JPEGs. Each round of JPEG compression loses detail. Always go back to the original image.

A quick checklist before uploading

1. The file is under the limit, with a little headroom. Some portals count 1 MB as 1,000,000 bytes, not 1,048,576.
2. Every page is upright and in order.
3. Small print, stamps and signatures are still legible at 100% zoom.
4. The file name is descriptive, for example Lastname_BankStatement_Mar-Apr.pdf.