PDF objects and streams
The optimizer generates efficient object streams, compresses compatible streams and recompresses eligible Flate data.
Optimize PDF tool
Compress PDF Online
Reduce PDF file size with a quality level suited to email, web upload, archiving or mobile sharing.
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75 MB per PDFStep 2 · Review and settings
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PDF optimizer
What PDF compression actually changes
PDF compression can reorganize object streams, recompress eligible data and optimize embedded images. It does not need to turn every page into a picture, and it should not be treated as a guarantee that every PDF will become dramatically smaller.
JPEG optimization
Recommended and Maximum can optimize embedded images using different JPEG quality settings. Maximum uses the stronger setting.
Text, vectors and fonts
Selectable text and vector artwork are not intentionally rasterized. The workflow does not claim to subset or remove embedded fonts.
Choose intentionally
Light, Recommended and Maximum compression
The labels describe the tradeoff—not a promised percentage. Actual savings depend entirely on the source PDF.
Light compression
Prioritizes visual fidelity. It optimizes PDF structure without the stronger image-optimization step used by the other profiles.
Good for:Archiving copies, print review and PDFs with important photographs.Balanced compression
Optimizes eligible images with a moderate JPEG quality setting while applying structural compression.
Good for:Email, web uploads and general document sharing.Maximum compression
Uses stronger JPEG optimization for the smallest practical output, with a greater chance of visible image artifacts.
Good for:Mobile sharing or strict upload limits after careful review.The source matters
Image-heavy, text and scanned PDFs behave differently
Image-heavy PDFs
Photographs, screenshots and full-page artwork usually offer the largest opportunity for reduction. JPEG recompression can lower size, but fine texture, gradients and small labels may show artifacts first.
Text and vector PDFs
Born-digital reports can already store text and vectors efficiently. Structural cleanup may help, but a small text PDF may have little avoidable data.
Scanned PDFs
Each page is commonly one large image. Compression can reduce those images, but excessive JPEG compression may soften scanned text. If the scan is image-only, run OCR PDF when searchable text is also required.
Quality factors
Resolution, JPEG quality and embedded fonts
- Image resolution and DPI
- More pixels usually mean a larger source. The current compressor does not promise a fixed output DPI, so check fine print at useful zoom and print a demanding page when print quality matters.
- JPEG compression
- JPEG is lossy: stronger compression discards more image detail. Recompress from the untouched original rather than repeatedly compressing an already compressed result.
- Fonts and subsets
- Embedded font programs can add size. The optimizer may improve surrounding PDF structure, but this workflow does not promise font subsetting, font removal or font substitution.
- Expected quality effects
- Light should cause the least visual change. Recommended can introduce subtle image changes. Maximum may produce blockiness, halos or softer scan text depending on the source.
Starting points
Recommended compression by use
These are workflow recommendations, not guaranteed outcomes. Download and inspect the real result before sending or archiving it.
Start balanced, then use Maximum only if an attachment limit still blocks the file.
Balances readable content with a smaller transfer for most forms and portals.
Keep the untouched original and favor fidelity. Compression alone does not create PDF/A.
Use Maximum only after checking small text and image detail on the downloaded file.
When size does not fall
Some PDFs cannot be reduced significantly
An already optimized PDF, a document made mostly of efficient text and vectors, or a file containing pre-compressed images may offer little safe reduction. If the generated file is not smaller, the application retains the original file size rather than returning a larger “compressed” result.
Troubleshooting
Check the output, not only the percentage
The PDF barely changed size
It may already be efficient. Removing pages with Split PDF or simplifying source images can help more than repeated compression.
Scanned text looks soft
Return to the untouched source and choose Light. Avoid compressing a previously compressed output again.
The PDF will not open
Check whether it is encrypted or damaged. Use an authorized unlocked copy, or try Repair PDF when the source itself is malformed.
A merged file is too large
First verify the combined document, then compress it once. If individual components are oversized, compress them before using Merge PDF.
Compression questions
Frequently asked questions
Which compression level should I choose?
Recommended is the sensible starting point for most PDFs. Use Light when image detail matters most, or Maximum when file size matters more and you can accept stronger JPEG recompression.
Will compression make text blurry?
Selectable text and vector graphics are not intentionally rasterized. Text already embedded inside scanned page images can soften when those JPEG images are recompressed.
Why did my PDF barely get smaller?
The file may already be optimized, contain mostly efficient text and vector objects, or use images that cannot be recompressed usefully without unacceptable quality loss.
Does compression change image resolution or DPI?
The current profiles optimize eligible images and apply different JPEG quality settings, but they do not promise a particular output DPI. Inspect image-heavy and scanned pages after downloading.
Can I compress a password-protected PDF?
The optimizer must be able to read the PDF. If you know the password and are authorized, unlock a copy first, compress it, and protect the result again if required.
Are fonts removed during compression?
The optimizer can clean and recompress PDF structures, but this workflow does not promise font subsetting or removal. Embedded fonts may limit how much a text-heavy PDF can shrink.
Why does the result sometimes stay the same size?
If optimization creates a file that is not smaller, the service preserves the original PDF bytes instead of making you download a larger replacement.
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