It seems mupdf stores the pages we view at memory and don't free them. In the beginning it uses just a little memory. Reproducible: Always Steps to Reproduce: 1. Open some big pdf file. 2. Page Down many times. 3. Actual Results: MuPDF uses almost 1 GB of RAM, MuPDF stores the pages on RAM and don't free them. Expected Results: The expected is that MuPDF just use the memory necessary to open the pdf files, and the present page.