Large PDFs are a constant problem — they bounce back from email servers, time out when uploading to web portals, and fill up storage faster than expected. Here are ten practical techniques to reduce PDF size, from quick fixes to more advanced methods.
The fastest solution for most people. Our Compress PDF tool reduces file size in seconds with no software needed. Select your compression level and download the optimised file instantly.
Images are the biggest contributor to PDF file size. A document with 300 DPI images destined for screen viewing only is carrying 4x more data than necessary — 72-96 DPI is sufficient for screen display. When compressing, our tool automatically downsamples images to match your selected quality level.
Scanned PDFs store each page as a high-resolution image. Running OCR and saving as a text-layer PDF can significantly reduce size while adding the bonus of making the document searchable. Use our OCR PDF tool for this.
Blank pages, placeholder pages and boilerplate appendices add weight without value. Use our Split PDF tool to extract only the relevant pages before sending.
Interactive PDF forms with unsubmitted fields carry extra data structures. After filling in a form, flatten it by printing to PDF or using our Fill PDF tool — flattening embeds the filled values and removes the interactive overhead.
PDF/A (archival format) embeds all fonts, colour profiles and metadata for long-term preservation — this makes files larger. Use PDF/A only when required for legal archiving. For everyday document sharing, standard PDF is smaller.
Documents that are primarily text-based look identical in greyscale. Converting colour pages to greyscale before creating the PDF can reduce size by 30-60% for scanned documents.
For very large documents (100+ pages), split into sections, compress each section, then merge the compressed sections back together. This two-step process sometimes achieves better overall compression than compressing the full document at once.
Every time a PDF is opened, edited and saved in some applications, internal redundancy accumulates. A PDF that has been saved 20 times can be noticeably larger than the original. Re-compress periodically to remove this accumulated overhead.
When creating PDFs from scratch, embed photos as JPEG (smaller, lossy) and diagrams or screenshots as PNG (larger but lossless for crisp edges). Using the wrong format for the wrong content type inflates file size unnecessarily.