Compress PDF
Reduce file size while keeping your PDF readable. Shows before and after size.
Compression Levels Explained
- Lossless — Re-packs the internal PDF structure using object streams. No pixels are changed. Typical saving: 5–20% depending on how the original was created.
- Medium — Re-renders each page to a JPEG at 72% quality. Typical saving: 40–70%. Good for sharing documents where slight quality reduction is acceptable.
- Strong — Re-renders at 45% JPEG quality. Typical saving: 60–85%. Best for very large PDFs where file size is the priority.
When Is PDF Compression Useful?
PDF files can grow surprisingly large when they contain high-resolution scans, embedded fonts or complex graphics. Email providers often reject attachments over 10–25 MB. Cloud services charge by storage. And slow internet connections make large PDFs painful to share. Compressing a PDF before sending or uploading saves time and money. PDFForge shows you the before and after file size so you can see exactly how much space you saved.
Compression Workflow: Compress Last, Not First
The best practice when working with PDFs is to perform all editing operations — merging, splitting, rotating, removing pages — on the original uncompressed files, and only compress the final document as the last step before distributing or archiving it. This is because some operations (especially Medium and Strong compression) convert pages to images, which can make subsequent operations less effective. For example, compressing a PDF and then trying to merge it may produce a larger result than merging first and compressing once at the end. Think of compression as the finishing step, not the starting point.
Why Some PDFs Are Enormous
PDF file size is mainly determined by the images it contains. A single high-resolution photo scanned at 600 dpi can be 5–15 MB on its own; a 50-page scan at that resolution easily reaches 300–400 MB. Vector graphics (charts, diagrams, logos) are typically very small. Text with embedded fonts adds a modest amount. The biggest culprit in oversized PDFs is almost always uncompressed or minimally compressed image content — exactly what the Medium and Strong compression modes target. If you have a PDF from a phone scanner app, the app may have used very high resolution settings to produce a "high quality" scan; the PDFForge compressor can often reduce this by 70% or more with no visible difference in readability.
Frequently Asked Questions
Will compressing a PDF change its content?
The Lossless mode never changes any pixels. The Medium and Strong modes re-render pages as JPEG images, which may slightly reduce the sharpness of fine text and images — this is the same trade-off every PDF compressor makes.
How much smaller will my PDF be?
The size reduction depends entirely on what's inside the PDF. A PDF that already contains compressed images may not shrink much. A PDF of high-resolution scans can often shrink by 70–85% on the Strong setting.
Why is my compressed PDF actually bigger?
This can happen with PDFs that already contain heavily-compressed images. Re-rendering them at 72% JPEG can sometimes produce a file that's slightly larger than the original. In that case use the Lossless setting, or the file is already as small as it can reasonably get.
Which compression setting should I use for scanned documents?
For scanned documents, Medium or Strong compression typically works very well because scans are rendered page-by-page anyway. The visual difference between a scanned page at 72% JPEG and the original scan is usually imperceptible to most people. Start with Medium and check the result; use Strong only if you need the smallest possible file.
Does compressing a PDF affect its text searchability?
In Lossless mode, text layers are fully preserved and the PDF remains searchable. In Medium and Strong modes, the page is re-rendered as an image — any text layer that existed becomes part of the image, so the PDF will no longer be searchable or copy-pasteable after compression. If preserving text searchability is important, use Lossless mode only.