A Brief History of PDFs and Why Compression Matters
The Portable Document Format or PDF has become the standard for document sharing and archiving across devices and platforms. First introduced by Adobe in 1993, PDFs revolutionized how digital documents could retain formatting, fonts, images and layouts intact regardless of the underlying software or hardware.
Over years, PDFs have grown more complex with support for multimedia, javascript, forms, annotations etc. This has often resulted in large file sizes especially for scanned documents, papers with lots of images etc.
Sending large files can be cumbersome and cost bandwidth. Compression algorithms reduce file size without adversely affecting quality. The ability to compress PDFs manually gives more control over final file size and quality.
Lossless vs Lossy PDF Compression
There are two main types of compression algorithms:
Lossless – As the name suggests, all data from the original file is retained. Image and text quality remain intact. Common lossless techniques like run-length encoding and Huffman coding can reduce text-heavy PDFs by upto 10-20%.
Lossy – Some data loss is acceptable to gain higher compression. Often used for images, lossy techniques like JPEG compression lead to some quality loss. Fine for low resolution images in PDFs. Text compression remains lossless. Overall file size can be reduced upto 90% in some cases.
Most manual PDF compression tools use intelligent hybrid algorithms balancing both lossless and lossy techniques for best results. Let‘s look at 3 popular ways to compress PDFs on your own:
1. Using Preview on Mac
Preview is the default app for viewing images and PDFs on Mac. Lesser known is its ability to export and compress PDFs with a few clicks.
Step 1: Open the PDF in Preview app. You can also drag and drop a file onto the Preview icon in Dock.
Step 2: Once open, go to File > Export in menu bar.
Step 3: Save the PDF file to a new name. In the Quartz Filter dropdown, choose Reduce File Size and hit Save.
That‘s it! The exported PDF will be optimized and compressed for size reduction. You can reopen and check for any quality changes.
Pros
- Simple interface and quick compression
- Retains searchability and edits
- Can recompress multiple times
Cons
- Limited to Mac only
- Basic control over compression levels
Preview compression works best for moderately sized documents. For advanced control, an online or desktop tool would be better.
2. Using Adobe Compress PDF Online
Trust Adobe, who created the PDF format, to have some great optimization tools. Adobe Compress PDF is a free web app that can compress PDFs upto 5MB.
Step 1: Go to adobe.com/acrobat/online/compress-pdf
Step 2: Click on Select a file and upload your PDF. Wait for it to process
Step 3: Choose compression level – High, Medium or Low depending on output quality needed. Hit the Compress button.
Step 4: Download the optimized PDF file. Quality remains fairly decent even at High compression.
This online tool makes it easy to optimize PDFs from anywhere without installing software. Ideal for occasional compression needs.
Pros
- Free and accessible online
- Good compression
- Files upto 5MB
Cons
- File size limited to 5MB
- Need to upload and download PDFs
For advanced use cases, Adobe Acrobat desktop app offers top-class compression.
3. Using Adobe Acrobat on Desktop
Adobe Acrobat Pro DC is considered the gold standard for working with PDF documents. It has excellent optimization tools built-in with fine grained control.
Step 1: Open the PDF file in Adobe Acrobat Pro app. Go to Tools > Optimize PDF.
Step 2: Select the opened file and click OK. The Optimize view opens.
Step 3: Go to Settings pane on the right and toggle Reduce File Size option. Choose compression level from dropdown.
Step 4: Click the icons to compress images, fonts etc. Ensure options like searchability are not disabled.
Step 5: Finally click the Apply Changes icon and save optimized PDF.
Acrobat gives granular control over PDF optimization settings compared to other tools. Ideal for advanced use cases with under the hood tuning options.
Pros
- Industry leading compression levels
- Lossless text compression
- Advanced settings control
Cons
- Paid software
- Steeper learning curve
Factors Affecting PDF File Size
What makes some PDFs much larger? Here are some common culprits:
- High resolution images
- Fonts not embedded/subset
- Scanned pages at non-OCRed
- Encrypted documents
- Web links, attachments
- High index structure overhead
Optimizing these areas before compression leads to better file size reduction.
Striking an Optimal Balance
Manual compression gives flexibility but needs you to test quality/size tradeoff. For documents requiring printing or OCR accuracy, lossless compression is safer. But for web usage or archival, smaller files work better.
Get best results by selective compression of images, fonts etc. rather than blind compression. Finally, always check the output legibility before widely sharing a compressed PDF.
Wrapping Up
Compressing PDF files to reduce size for sharing is simple with the right desktop or online tools. Each technique has its own pros and cons. For occasional needs, use Preview or Adobe Compress. For advanced use cases, invest time mastering Adobe Acrobat.
Remember, excessive compression can affect text quality so test files before use. With the right optimization settings, you can safely reduce PDF sizes upto 80-90% in some cases.
Implement these handy PDF compression skills to send documents faster and take control over file bloat! Have any other tips? Share them in comments below!
