How to Compress a PDF to Reduce File Size
June 28, 2026 · 3 min read
Large PDF files are difficult to share. Email providers typically reject attachments over 25 MB, cloud storage fills up quickly, and slow internet connections make downloading bulky files frustrating. PDF compression reduces the file size so your documents are easier to send, upload, and store — without losing the content that matters.
Why are some PDFs so large?
The size of a PDF depends on what it contains. Text-only documents are usually small — a 100-page text document might be under 1 MB. But PDFs that contain images, scanned pages, embedded fonts, or vector graphics can easily reach 50 MB or more. Here are the most common reasons a PDF ends up larger than expected:
- High-resolution images: Photos and graphics embedded at full resolution are the biggest contributor to file size. A single uncompressed photograph can add several megabytes.
- Scanned documents: When you scan paper documents, the scanner saves each page as an image, resulting in much larger files than text-based PDFs.
- Embedded fonts: PDFs can embed the full font files used in the document to ensure consistent display. Multiple fonts or large font families increase file size.
- Redundant data: Some PDF generators include duplicate objects, unused resources, or unoptimized internal structures that inflate the file without adding visible content.
How PDF compression works
PDF compression typically involves several techniques applied together:
- Image resampling: High-resolution images are downscaled to a resolution appropriate for screen viewing (usually 150 DPI instead of 300+ DPI). This alone can reduce file size dramatically.
- Image recompression: Images are re-encoded using more efficient compression algorithms like JPEG for photos or JPEG2000 for mixed content.
- Object deduplication: Identical objects (like repeated logos or backgrounds) are stored once instead of being duplicated across pages.
- Stream compression: The internal data streams of the PDF are compressed using algorithms like Flate (zlib) compression.
- Removing metadata: Stripping unnecessary metadata, thumbnails, and bookmarks can save additional space.
How to compress a PDF with techyworks
- Step 1 — Open your PDF: Visit techyworks.online and load the file you want to compress.
- Step 2 — Open the compress tool: Click the "Compress" option in the toolbar.
- Step 3 — Choose a compression level: Select between light, medium, or strong compression depending on how much you want to reduce the file size. Stronger compression produces smaller files but may reduce image quality.
- Step 4 — Compress and download: Click compress and download the smaller file. The compression runs locally in your browser.
Compression trade-offs
There is always a trade-off between file size and quality. Light compression preserves the highest image quality but offers modest size reduction. Strong compression produces the smallest files but may introduce visible artifacts in photographs. For documents that will only be viewed on screen — such as email attachments or web downloads — medium compression usually provides the best balance.
If you plan to print the document at high quality, use light compression or no compression at all. Print requires higher resolution images (300 DPI), and heavy compression may produce noticeable blurring or banding in printed output.
How much can you save?
The amount of compression depends entirely on the original content. A PDF full of high-resolution photographs might shrink by 60-80% with medium compression. A text-heavy document with few images might only shrink by 5-10%, because there is not much to compress. Scanned documents often see the most dramatic reductions, since each page is a large image that responds well to resampling.