Compress PDF helps reduce a document's file size. Some PDFs can become big, making sending them to other users over the internet challenging. Compressing the PDF makes it smaller and reduces the complexity of sending your contracts or applications through e-mail. Uploading documents on the web is also simpler for small-sized documents. What is PDF Compression? PDF compression involves reducing a PDF file's size. You can reduce the size of a document by reducing the image quality. The process is as simple as changing those images' DPI and can reduce a file's size by almost half. To share your PDF files online easily, you should consider PDF compression.