Why Compress a PDF?
PDF documents can grow surprisingly large, especially when they contain high-resolution images, embedded fonts, or complex vector graphics. A 50-page report with photographs can easily exceed 100 MB, making it impractical to email, upload to a portal, or share through messaging apps that impose file size limits. Compressing your PDF reduces the file size so it fits within those constraints while keeping the document readable and visually acceptable. Common scenarios include sending attachments via email (most providers cap at 25 MB), uploading to government portals or job application systems with strict limits, sharing documents on mobile where bandwidth and storage are limited, and archiving large collections where cumulative storage adds up quickly.
How the Compression Process Works
ConvertKr's PDF compressor works by rendering each page of your original PDF as a JPEG image at a resolution of 1.5x the page dimensions, then embedding those JPEG images into a brand-new PDF document. The key variable is the JPEG quality setting, which controls how aggressively the image data is compressed. A quality of 0.3 (Low) produces heavily compressed images with noticeable artifacts but dramatic file size reduction. A quality of 0.9 (Ultra) produces images that are virtually indistinguishable from the original with moderate size savings. The sweet spot for most users is Medium (0.5), which typically achieves 50-70% size reduction while keeping text legible and images clear.
Choosing the Right Quality Level
The ideal quality level depends on your document's content and your intended use. For text-heavy documents like contracts, reports, and articles, even Low quality usually produces perfectly readable results because text edges remain sharp in JPEG compression. For documents with photographs, charts, or detailed illustrations, Medium or High is recommended to avoid visible compression artifacts around color gradients and fine details. For print-quality output where you need the compressed file to look as close to the original as possible, use Ultra. You can always compress the same file at multiple quality levels to compare the results and find the setting that works best for your specific document.
Trade-offs and Considerations
It is important to understand that this compression method converts each page into a raster image, which means the output PDF will no longer contain selectable or searchable text. If you need to preserve text selectability — for instance, for accessibility or for documents that will be indexed by search engines — this tool may not be the right choice. However, for the vast majority of use cases where the goal is simply to produce a smaller file for sharing or archiving, the image-based approach delivers excellent results with predictable, consistent compression ratios across all types of PDF content. The original file is never modified, so you can always keep it alongside the compressed version.