Currently in the country, used to generate PDF documents are the main tools for Adobe's Acrobat Distiller, PDFLib open source database, as well as some results can produce a virtual PDF printer tools. These tools generate PDF documents in the process, more or less there will be some small problems. Acrobat Distiller in the production of PDF documents, for the black and white images do not use a higher compression ratio JBIG2 encoding, but the use of coding CCITTFax; PDFLib making use of PDF documents, sometimes in the paper a lot of useless objects (these objects have never been invoked, it is spam, in the most extreme cases, the spam files occupy half of the total size).

      As we all know, is not only larger files take up more storage resources, but also spend more time to download. For those who e-books in PDF format for enterprise data services, to existing PDF file compression can not only save storage space, but also the speed of encrypted data and, more importantly, they can improve the quality of business services .

     PDF compression, mainly from the following aspects of dealing with PDF documents:
       1, did not use JBIG2 compression for black and white images, all encoded using JBIG2 compression; can use lossless compression, lossy compression can also be used (there are four levels of lossy compression options). When using non-destructive compression, PDF file will remain the same as the original document and the quality of the show.

       2, for the use of JPEG-encoded color image or gray image, all converted to JPEG2000 encoding can greatly reduce the file size.
       3, for the use of LZW compression coding content, is replaced with Flate compression. Early on the PDF file using LZW coding more.
       4, removal of the object has never been invoked,
       5, in accordance with the PDF specification, with a view to saving space, the contents of the documents the form of organization.
       6, the combined object. Comply with the PDF specification, will be the subject of a number of small mergers, in order to save space.
       7, have not been encoded and the length of the stream is greater than 100, use Flate encoding;
       8, compressed cross-reference tables and document structure. PDF pages for more documents, in describing the structure of their documents, will take up a lot of space, especially for most of the contents of a text document, and its compression efficiency is considerable. The most typical example is Adobe's PDF format specification, the compressed size of 8.276 trillion, if we do not use compression and document cross-reference table structure, the size of more than 17 trillion. The use of compressed file in this manner Acorbat Reader6.0 need to open later.

         For black-and-white images include PDF documents can be compressed to reduce one of nearly 4 points in space. Some can even reach one-half of documents. With regard to color or gray image-based PDF documents, the size of the compressed compression can be reduced to one-fifth or more of the former.