Quick answer
Compress the PDF first: most oversized uploads are scans or photos, and lowering image resolution to about 150 dpi usually cuts them by half or more. If it is still too big, remove pages the portal doesn't need or split the file into parts. Aim a little below the stated limit, since some portals count megabytes differently.
Online forms are strict about file size. Job applications, university portals, visa and immigration systems, insurance claims and benefit applications often accept PDFs of only 1, 2, 5 or 10 MB. Meanwhile a phone scan of a three-page passport application can easily reach 15 MB. The portal simply says "file too large" and gives no advice.
This guide shows how to get a PDF under an upload limit in the right order: compress first, cut pages second, split last. It also covers free methods built into your computer or phone, and the mistakes that make a document unreadable for the person who reviews it.
Why upload limits are so small
Upload portals are often old systems that store every attachment for years. Small limits keep their storage and review queues manageable. Email allows around 20–25 MB per message; upload forms are usually much stricter. Typical limits look like this:
| Where you upload | Typical PDF limit | What usually works |
|---|---|---|
| Job application systems | 2–5 MB per file | Compress at Recommended |
| University and school portals | 2–10 MB per file | Compress; split long transcripts |
| Visa and immigration forms | 1–4 MB per file | Compress at Strong, scan in grayscale |
| Insurance and benefit claims | 5–10 MB per file | Compress; one PDF per document type |
| Court and government e-filing | Varies, often 10–35 MB | Follow the court's own PDF rules |
These are typical ranges, not rules. Always use the number printed on the upload page.
What makes your PDF too big
Almost every oversized upload has one of three causes.
- A scan at high resolution. Scanners and scanning apps default to 300–600 dpi in full color. A page of plain text doesn't need that much.
- Phone photos placed in a PDF. A modern phone photo is 12 megapixels or more. Turned into a PDF page, it keeps every one of those pixels.
- Several documents merged together. Ten 1 MB scans make a 10 MB file, and a 5 MB limit stays a 5 MB limit.
Typed documents exported from a word processor are rarely the problem. A 20-page letter is usually well under 1 MB. If yours is large, it probably contains big images.
Step by step: shrink the PDF with MyPDFDone
- 01Find the exact limitRead the upload page for the maximum size per file and the allowed formats. Note whether the limit is per file or for all uploads together.
- 02Upload the PDF to Compress PDFOpen MyPDFDone's Compress PDF tool and drop your file on the upload box. Files up to 100 MB are accepted.
- 03Choose a levelStart with Recommended. If the result is still above the limit, run the original again with Strong. Use Light only if the file must be printed.
- 04Check the size and the previewThe new size and a preview are shown for free. Zoom into small print, signatures and stamps to make sure the reviewer can still read them.
- 05Download and upload to the portalIf it looks right, download the smaller file for $2.99, paid once, and upload it. If it is still too big, split it or delete pages you don't need.
Uploading, compressing and previewing are free, so you can see the exact new size before deciding anything. If you download, it's a one-time $2.99 for that file, not a trial that turns into a subscription. If a file can't get any smaller, MyPDFDone tells you it's already optimized rather than handing back a bigger file.
Which level should you pick?
Recommended keeps images at about 150 dpi, which is clear on screen and fine for ordinary printing. Strong goes down to about 72 dpi: good for very strict limits like 1–2 MB, but small print in scans gets soft. If you need Strong, always compress the original, not an already compressed copy, because each round of compression loses a bit more detail.
If it is still too large: cut pages, then split
When compression alone isn't enough, look at the content before you reach for more aggressive settings.
Remove pages the portal doesn't need. Blank backs of single-sided pages, cover sheets, instructions you scanned by accident and duplicate pages all add weight. Take them out with Delete PDF pages by typing their numbers, for example 2,4-6.
Split into separate uploads. Many portals allow several files, one per document type: one for your ID, one for your diploma, one for references. Split PDF cuts a file by page ranges such as 1-3,4-7, and you get a ZIP with one PDF per range. Name each part clearly, for example "Smith-diploma.pdf" instead of "scan0001-part2.pdf".
Rescan at a lower setting. If you still have the paper, a fresh scan at 200 dpi in grayscale is often smaller than any compressed version of a 600 dpi color scan, and it looks cleaner.
When the portal wants one file for everything
Some forms have a single upload box for "supporting documents" with a single size limit. In that case the order of operations matters:
- Put the pages in the order the reviewer expects, usually the order of the checklist on the form.
- Merge the separate PDFs into one file.
- Compress the merged file once, then check the size.
- If it's still too big, remove optional pages (extra copies, blank pages, instructions) rather than pushing compression further.
Compressing each file separately and then merging works too, but you end up checking quality several times, and merged files can carry duplicate fonts and images that a final compression pass removes.
Free ways to shrink a PDF on your device
You don't always need an online tool. These built-in options work, with some limits.
Windows
Windows has no built-in PDF compressor. If the PDF came from a document you wrote, re-export it from the original app and choose the smaller or "minimum size" option in the save dialog, which lowers image resolution. For scans, lower the resolution in your scanner software (200 dpi, grayscale) before saving the PDF.
Mac
Open the PDF in Preview, choose File > Export, and pick the "Reduce File Size" Quartz filter. It is free and fast, but very aggressive: it can make scanned text blurry and photos blocky. Check the result closely before uploading, and keep the original.
iPhone and iPad
When you scan with the Notes or Files app, you can't choose the resolution, but scans in grayscale or black-and-white are much smaller than color ones. Choose the filter before saving. For an existing large PDF there is no built-in compressor; use a browser-based tool from Safari.
Android
Scans made with the scan feature of a cloud storage app are usually already compressed. If a camera photo needs to become a PDF, take the photo at a lower resolution setting, or crop it tightly first so less of the image is stored.
Mistakes to avoid
- Compressing a compressed file. Every round makes images worse. Keep the original and compress from it each time.
- Taking a screenshot of each page. Screenshots look fine on your screen but are often blurry when the reviewer zooms in, and they lose any real text.
- Renaming the file to .jpg or .zip. It doesn't change the size and the portal may reject or corrupt it.
- Sending a password-protected file. Many portals can't open encrypted PDFs and silently reject them. If your file has a password you know, remove it first; see how to remove a password from a PDF.
- Forgetting the reviewer. A file that passes the size check but can't be read may get your application returned. Zoom in on the preview.
A quick check before you press Upload
- The file is a little below the stated limit, not exactly at it.
- Every page is upright and in the right order.
- You zoomed into the smallest text, signatures and stamps, and they are legible.
- The file name says what the document is.
- The PDF has no password, unless the portal asked for one.
If you're sending the same document by email instead of uploading it, the limits and the tricks are slightly different; see how to reduce PDF file size for email. And if the portal needs one combined file, start with how to merge PDF files into one and compress the result.
Frequently asked questions
Some systems count a megabyte as 1,000,000 bytes and others as 1,048,576, and some include form data in the total. A 4.9 MB file can fail a 5 MB check. Aim for about 90% of the stated limit to be safe.
Usually not. Typed text is stored as font outlines and stays sharp at every level. Scanned pages and photos lose some fine detail, which is why you should zoom into the preview before uploading.
Only if the portal accepts ZIP files, and most document portals don't. A ZIP also saves very little on a PDF, because the contents of a PDF are already compressed internally.
Merge them into one PDF first, then compress the merged file. Merging first means you only check the quality and the size once.
No. Compression changes how images are stored; it does not remove text, signatures or filled-in values. If a signature was added as an image, check it in the preview, since it is the detail most likely to soften.
Check how the service treats files. MyPDFDone sends files over HTTPS, keeps them in private storage and deletes them automatically 2 hours after upload. Nobody opens them, and they are never used for training.