How to Compress a PDF Without Losing Quality

How the compressor works

Scanned pages and photos are what make most PDFs big. A phone or office scanner can store each page as a several-megapixel image, far more pixels than a screen or printer needs to show a page of text clearly.

NovaPDFTool redraws every page as an image at up to 150 DPI, saves it as a JPEG at the quality you choose, and builds a new PDF from those images at the original page sizes. Two things follow:

• Big scans shrink dramatically, because 300 DPI pages come down to 150 DPI or less.
• Text turns into a picture of text. It can no longer be selected or searched, links stop working, and a PDF that was mostly typed text would get bigger, so for those the tool keeps your original instead.

How to compress a PDF, step by step

1. Open the compressor. Go to novapdftool.com/compress on a computer or phone.
2. Add your PDF. Drop one PDF onto the box or click Browse files. Its name and current size appear underneath.
3. Choose how small. If you have a size limit, type it under Customised Size and choose KB or MB. Otherwise pick a preset: Low Compression, Recommended or Extreme Compression.
4. Click Compress file. A progress bar shows each stage. When it finishes, the final size appears, or a warning if your target was too small to keep the pages readable.
5. Download and check. Click Download, open the file, and zoom in on the smallest text before you send it. Keep your original PDF.

What we measured on a scanned document

How we tested: we ran the live NovaPDFTool code in Chrome 155 on a Windows laptop (Intel Core i5-12450H, 16 GB RAM) on 17 October 2026, using sample files we built for testing. Times are the middle of three runs. A phone or an older computer will take longer, so treat the times as a comparison between settings, not a promise. The main file was a 10-page colour scan at 300 DPI (A4) of 18.43 MB, the kind of file a scanner app produces. The 100 KB row is from a single run.

Every Customised Size result stayed under its target. The 100 KB target couldn't be met: the tool showed a warning and handed back the smallest file it was willing to make, 160.1 KB.

How the pages looked

We converted page 1 of each result back to an image and compared the same lines of small print against the original scan:

• Low and Recommended: we couldn't tell them apart from the original at normal size. This is the "without losing quality" range.
• Extreme and the 500 KB target: easy to read, with slightly rough edges on letters when you zoom in. Fine for forms and receipts.
• The 160.1 KB fallback: headings were fine, but small print was blurry and some figures were hard to tell apart. If a file this small carries amounts, dates or ID numbers, check every one of them.

Choosing a compression level

• Low Compression saves JPEGs at 85% quality. Use it for pages with photos or fine diagrams.
• Recommended saves at 60%. On A4 and Letter pages it keeps the same 150 DPI as Low, so the only difference is JPEG quality, and it gave a file less than half the size of Low. Start here.
• Extreme Compression saves at 35% and also caps the longest side of each page at 1200 pixels, about 100 DPI on A4. Best for paperwork where legibility matters and sharpness doesn't.

Presets are a single pass, so they're the fastest option. Large pages are capped too: Recommended limits the longest side to 2000 pixels, Low to 2600.

Hitting an exact size limit

When a form or email has a limit, type it into Customised Size. Gmail, for example, caps attachments at 25 MB. If the file is already under your number, you get it back unchanged. Otherwise the tool searches for the best result that fits:

1. It draws every page once at 150 DPI.
2. It tries page sizes from largest to smallest (a longest side of 2000, 1600, 1200, 900 and finally 700 pixels) at the lowest quality, 30%, until one fits under your target.
3. At that size, it builds real test files seven times, raising the JPEG quality as far as it can without going over your target, and keeps the best one.

That's why a target takes about twice as long as a preset, and why the result lands just under your number. It never goes below 700 pixels at 30% quality. Below that, text breaks up, so if your target is smaller than that floor, you get the warning and the smallest file at the floor instead.

Don't compress text-only PDFs

A PDF exported from Word or Google Docs stores text as text, which takes almost no space. Turning those pages into images makes the file bigger: in our first test, a 20-page text report of 28.8 KB came out at 2.26 MB on Recommended, 80 times bigger. The tool now compares every result with your original and keeps the original whenever compressing wouldn't make it smaller. We ran the same report through it again:

When the original is kept, there's no download, because the file you already have is the smallest version. The tool still has to try first, so it takes a few seconds before telling you. So check the size before you start. If a text PDF is already small, it doesn't need compressing. If it's large, the weight is usually in embedded photos, and compressing will help, at the cost of selectable text.

Photo PDFs shrink the most

PDFs made from phone photos are the best case. Four 12-megapixel photos turned into a 17.45 MB PDF with Images to PDF came down to 666.9 KB on Recommended in 1.2 seconds, small enough for nearly any email limit.

Before you send the file

• Open it and zoom in on the smallest text, especially numbers and signatures.
• Keep the original. Detail removed by compression can't be brought back from the smaller copy.
• Need the text searchable again? Run the compressed file through OCR PDF.
• Still too big at a readable quality? Send it in parts with Split PDF.