Reduction in the file or data size refers to compression of the PDF file. Compressed version can save storage space and takes less time to be attached with emails and transfer through the Internet. In addition, compressed PDF file makes it easier and much faster for the recipient of the email to download the attachment. Reduction of data of PDF files can be implemented by compressing only the data content of the entire unit. Simple techniques such as removal of extra space characters and use of a single repeat character for a particular string of characters such as a word can shrink the file to half the original size. This is achieved by programs that use algorithms to fix ways to compress and decompress data. The strength of the algorithm is crucial to the quality of compression.
PDF files are designed to be loaded with graphics and other space consuming data. Thus, PDF files come with some built in compression functionality. Compression or reduction methods used on PDF can be either lossy or lossless. Lossy algorithms like JPEG compression can be used to shrink image and audio files, but they are not useful for text and program files since some information is lost in the compression process. For text and program files one must reduce the file size with the help of lossless compression algorithms where all the data can be restored on decompression.
To reduce PDF file size to the best degree possible, the user should prepare the bitmap images to be inserted in such a way that the dimensions are minimized. The user should also look out for the best quality images and use black and white images wherever possible. RGB color space works better for shrinking than CMYK. When color is not really needed, think of using grayscale. In addition, thumbnails should be turned off since vector based graphics generally work better than bitmap graphics. The user should avoid using too many fonts, since each additional font takes 40k in getting embedded.