Portable Document Formats, PDFs are the most prominent file formats used for sharing data. Due to the presence of a varied collection of files in various formats, the PDF file becomes bulky and defeats its purpose small file size. Compressing a PDF file becomes essential when looking to share or transfer the file.
The process of compressing a PDF file is a relatively easy and can be done within a few steps. They include the usage of the save-as command in the PDF editor and save the whole file instead of appending the existing file, which may cause an increase in the size of the file. Graphics and animations in the file are embedded at low resolutions instead of high resolution ones, images are replaces with text-only formats, using consistent file fonts, styles and colors, and finally, removing unnecessary things like named destinations, etc.
The process of compressing a PDF file can also be done by using free PDF compressors which basically edit the metadata of the PDF file. They remove repetitive parts in the metadata, replacing it with strings. Compressing a PDF file tends to remove unused parts of the metadata and also decreases the size of the file by reducing the resolution of the graphics, animations and images present in the PDF file.
Lastly, compressing a PDF file is done is by using loss-less and lossy algorithms. In these algorithms, the PDF file is decoded and broken down into bits, storing bytes sequences and corresponding ASCII values. By this ASCII value sequence, the decoding of data is done easily. Also, no part of the data is lost, making it more efficient. Lossy algorithms are used for this reason. The most popular algorithms that are used for compression are ZIP, CCITT, JPEG, JBIG2, LZW and Flate, among which JPEG alone is a lossy algorithm.