How to reduce PDF size without ruining readability
Understand resolution, image quality, grayscale and when raster compression is appropriate.
Find out what makes the PDF large
Scanned pages and full-resolution photographs are the most common reasons for a large PDF. Text-only PDFs generated by office software are usually already compact. Before compressing, compare the file size with the page count and check whether every page is a scan.
Resolution matters more than many people expect
A page rendered at twice the width and height contains roughly four times as many pixels. Reducing resolution can therefore save more space than aggressively lowering JPEG quality. For screen viewing and online applications, a balanced setting is usually enough. Print archives may need a higher setting.
Use grayscale for black-and-white paperwork
Color scans of monochrome documents store unnecessary color information. Grayscale can reduce size and often improves consistency. Do not use it when colored stamps, signatures, highlights or photographs are important.
Understand raster compression
Raster compression rebuilds each page as an image. It works well for scans, but searchable text, links, form fields, accessibility tags and digital signatures may be lost. Keep an original copy when those features matter.
Review the smallest text
After compression, zoom in on names, numbers and fine print. A file that is small but unreadable is not useful. If text looks soft or blocky, choose the next higher quality preset.