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Compression is a technique to reduce the file size for storage or transmission. Differences exist in the compression methods applied to storage and transmission. Every transmission unit has information added to it for route recognition and specific information added to identify the source and the target address. Compression can be applied to the content or the transmission details. Content compression identifies repetitive characters and maps it into a single character appended by number of occurrences. Number occupies lesser file space than characters. Characters with no or very less significance are embedded in the file for high quality imaging. This accounts for a substantial increase in the file size. Insignificant characters are identified and removed using specific algorithm during compression. Compression techniques use referencing to replace frequent occurrences of a particular combination with a legend, a less space occupying string to denote unique combination of characters. Strategy and logic employed in these methods have necessary algorithm to achieve an approximate fifty percent reduction in file size.

PDF, Page description language, is based on Postscript with trimmed functions to implement small file sizes and simplified functionality. PDF files are similar to Image files even though the content may contain only text. Compression algorithm for PDF files differs from the other file compressions. Since PDF files have been designed to be Image files, PDF file creators employ techniques to keep the file size relatively smaller than the Image files. Many standard compression algorithms are available and the popular among them are Run length Coding (RLE), JPEG, LZW etc.

Compression algorithms for PDF files follow two techniques that depend on the type of information stored in the file. Compression algorithms like JPEG provide good compression rate but the decompressed file reports loss of information. JPEG is best suited...