Compress PDF (Reduce File Size)

Why PDFs get so big

PDF size usually comes from images. A document scanned on a phone or office copier can store each page as a large, high-resolution photo, so a 10-page scan can easily reach 20-30 MB. Many job portals, government sites and email services limit uploads to 2, 5 or 10 MB, which makes compression essential.

Three compression levels

This PDF compressor offers three levels, and it tells you honestly what each one does:

• Basic cleans up the file structure and packs objects more efficiently. Text stays selectable and quality does not change. Savings are small and depend on how the PDF was made.
• Recommended turns every page into a 150 DPI JPEG image and rebuilds the PDF. This shrinks scanned and image-heavy PDFs a lot while staying easy to read and print.
• Strong uses 100 DPI and stronger JPEG compression for the smallest possible file. Good for screen viewing and strict upload limits.

Important: Recommended and Strong turn pages into pictures, so text can no longer be selected, searched or copied, and links stop working. For text documents that need to stay searchable, use Basic.

If a level cannot make your file smaller, the tool tells you and does not give you a bigger file.

How to compress a PDF

1. Choose or drop your PDF.
2. Select a compression level. Start with Recommended.
3. Click Compress PDF and watch the page counter.
4. Compare the before and after size, then download the result.

Other ways to make a PDF smaller

• Remove pages you do not need with Split PDF.
• Compress images before creating the PDF with the Image Compressor, then build the PDF with Image to PDF.
• Scan in grayscale at 150-200 DPI instead of color at 600 DPI.
• When exporting from Word, choose "Minimum size" or "Optimize for online".

Page rendering uses Mozilla's open-source PDF.js, the same engine that displays PDFs in Firefox. See all our PDF and image tools.

Typical upload limits

Many online forms set a maximum file size. Job portals and university admissions often allow 2 MB to 5 MB, government portals sometimes only 1 MB, and most email services stop at about 25 MB. If one file is still too big after compression, cut it into parts with Split PDF, or combine only the pages you need with Merge PDF.

Choosing the right compression level

Important: the Recommended and Strong levels turn pages into pictures. Text will look the same but can no longer be selected or searched. Keep your original file if you might need to copy text later.

Real-world result

In our own testing, a 3.84 MB scanned document dropped to 1.29 MB with the Recommended setting, about two thirds smaller, while staying easy to read. Results depend heavily on what is inside the PDF: scans and photos shrink a lot, while files that are already mostly plain text may only shrink a little.

How to hit a specific size limit

Portals often ask for files under 1 MB, 500 KB or even 200 KB. Try this order:

1. Run Recommended first and check the size.
2. If it is still too big, try Strong.
3. Still too big? Split the document with Split PDF and upload the parts separately, if the portal allows several files.
4. For documents made from phone photos, recreate the PDF from smaller images: compress the photos with the Image Compressor, then rebuild with Image to PDF.

Why scanned PDFs are so large

A scanner or phone app often saves every page as a high-resolution colour photo, sometimes 300 DPI or more, even for a black-and-white letter. A single A4 page at 300 DPI is about 2480 x 3508 pixels. For on-screen reading and most uploads, 150 DPI is plenty, which is a quarter of the pixels. That is where most of the savings come from.

Tips for smaller PDFs from the start

• Scan documents in greyscale unless colour is needed.
• Use 150 DPI for documents and 300 DPI only for photos that will be printed.
• When exporting from Word, choose "Minimum size" or "Standard" instead of "High quality print" when the file is for email.
• Avoid inserting huge photos into documents; resize them first with the Image Resizer.

All compression runs on your own device using PDF.js and pdf-lib, so confidential documents never leave your computer or phone.

Example: a scanned document for a job portal

A job portal asks for your degree as one PDF under 1 MB. Your phone scan app produced a 6-page file of 7.5 MB.

1. Add the file here and choose Recommended.
2. Check the new size. Scans like this often shrink to a quarter or less of the original.
3. If it is still above 1 MB, run the original again with Strong.
4. Open the result and zoom in on the smallest text, such as the registration number, to make sure it is still readable.
5. Upload the compressed copy and keep the original high-quality scan safe for printing later.

If even Strong is too large, remove pages the portal does not need, such as the back side of a certificate, with Split PDF and compress again.

Last updated: October 25, 2026