Reduce PDF file size
Unlike images (JPEG/PNG) which are grids of pixels, a PDF is a complex relational database of objects (fonts, vectors, text, images, and metadata). Compressing a PDF requires parsing this database and rewriting it more efficiently.
Older PDFs store every object individually, which creates a lot of overhead. This tool upgrades the PDF structure to use Object Streams.
This feature groups multiple objects together and compresses the entire group using the FlateDecode (zlib) algorithm, significantly reducing the file size of vector and text-heavy documents.
PDFs often contain invisible "orphan" objects—fonts that were embedded but are no longer used, or massive XML metadata payloads from creation tools like Adobe Illustrator.
The "High" compression setting aggressively traverses the document tree to strip out Document Information dictionaries and unreachable objects.
This tool performs structural compression, not image degradation. If your PDF is just a scanned document (a giant JPEG wrapped in a PDF envelope), the structure is already minimal.
To compress a scanned PDF further, you would need to lower the resolution or quality of the embedded image itself, which requires heavy raster image-processing algorithms that this structural tool does not attempt.
What is an 'Object Stream' in the context of a PDF file?
