PDF Compressor Online

PDF (Portable Document Format) is the universal standard for sharing documents that must look identical on every device and operating system. Created by Adobe in 1993 and standardized as ISO 32000, PDF encapsulates text, fonts, vector graphics, raster images, and interactive form fields in a single self-contained file. This versatility is also why PDFs can become unexpectedly large: a single document might contain high-resolution embedded photographs, multiple font subsets, vector illustrations, layers from design tools, and metadata — all contributing to file bloat. Scanned documents are particularly problematic because each page is stored as a full-resolution raster image rather than lightweight vector text. A 10-page scanned contract at 300 DPI in color can easily weigh 20-50MB, making it impractical to email or upload to portals with size limits. Even digitally created PDFs from Word, PowerPoint, or InDesign can grow large when they contain embedded high-resolution images, complex charts, or presentation slides with photographic backgrounds. PDF compression reduces file size by downsampling embedded images, optimizing internal object streams, removing duplicate data, and re-encoding content more efficiently — all while preserving the document's visual layout, selectable text, and interactive elements.

SizeSnap compresses PDFs using a multi-pass optimization pipeline. The first pass analyzes the document structure to identify the biggest opportunities for size reduction — typically embedded raster images, which often account for 80-95% of a PDF's file weight. These images are re-encoded at progressively lower quality levels using the same binary-search approach that powers SizeSnap's image compression: the algorithm iteratively adjusts image quality, re-builds the PDF, and checks the total file size until it lands within a tight tolerance of your target. Beyond image optimization, the pipeline applies stream compression, removes duplicate objects and unused resources, and optimizes the cross-reference table. The result is a PDF that maintains its original page layout, selectable text, hyperlinks, and bookmarks while meeting your exact size requirement.

• 1For email attachments, target 1-2MB for the best balance of quality and deliverability. Most corporate mail servers accept this size without issues.
• 2Scanned documents compress dramatically better in grayscale than in color. If color is not essential, convert to grayscale before or during compression.
• 3Text-heavy PDFs (reports, contracts, academic papers) can often be compressed to very small sizes with zero visible quality loss, since vector text takes minimal space.
• 4If your PDF contains form fields, flatten them before compressing — interactive form data adds hidden weight that persists even after visual compression.
• 5Always verify that compressed PDFs open correctly in multiple viewers (Adobe Reader, Chrome's built-in viewer, Preview on macOS) before submitting to important portals.

Will compression break my PDF’s links and bookmarks?

No, SizeSnap preserves hyperlinks, bookmarks, and selectable text. Only embedded image quality is reduced to meet the target size.

Can I compress a scanned PDF?

Yes, scanned PDFs often compress dramatically because they’re essentially full-page images. SizeSnap optimizes these embedded images to hit your target.

Is the compressed PDF still searchable?

If your original PDF has searchable/selectable text (not just a scanned image), SizeSnap preserves that text layer during compression.