Reducing for Bandwidth
The primary reason for reducing a PDF file's size is for bandwidth. While most internet users, especially in the United States, have broadband access, many still have dial-up. Just as important, the file size limitations of most internet service providers as well as internet presence providers (web hosts) will prevent large PDF file's from being transferred, especially through email. Perhaps, the greatest consideration for reducing a PDF file's size is that of web hosts. Many web hosts charge for both bandwidth and storage. Further, many email list applications send a separate email to each address on the list. With large and numerous files, reducing a PDF file's size can be a significant cost saving measure for an online presence.
Content of a PDF File
Before reducing a PDF file's size, it is helpful to understand the content of a PDF file. Originally created in 1993 as a proprietary format for document exchange, a PDF (Portable Document Format) file consists of one or more or even all three types of content - text, raster graphics, and vector graphics. Raster graphics are typically photographs or other artwork that are more difficult to compress. Vector graphics are graphics composed primarily of lines and shapes such as charts and graphs; these are more easily compressed into the file. There are also two types of layout that should be considered when reducing a PDF file's size - non-optimized, (non-linear) and optimized (linear). A non-linear layout will actually help with reducing a PDF file's size, but at the expense of slower access. However, an optimized layout enables the file to be read in a web browser.
Software to Reduce PDF Files
As the PDF file format became an open standard of the International Organization of Standards in 2008, software developers have been free to utilize the format in applications. Other than proprietary software, open source applications are available for reducing a PDF file's size. Further, due to the open standard, as additional applications are developed and existing programs improved, options for reducing a PDF file's size will become more available. However, removing non-essential objects from the document will go far in reducing a PDF file's size.