Why Adobe PDF Compression
When you have a large number of PDF files to be sent as an email attachment, or to be uploaded to a server, Adobe PDF compression comes into play. It compresses the PDF files so that they have a smaller size than the original. Adobe PDF compression is best used when you want to archive your PDF files. It reduces the storage space needed for these files on your hard disk, and helps in storing many numbers of files in the allotted space. Thus the compressed file is just a mirror image of the original, now with reduced size.
Adobe PDF Compression Algorithms
Adobe PDF compression uses various algorithms to compress the PDF files. The method you adopt depends on the kind of images you are compressing. The default adobe PDF Settings use automatic (JPEG) compression for color and grayscale images and CCITT Group 4 compression for monochrome images. In addition to this, resampling bitmap images reduces the file size. The process is also called downsampling as it reduces the number of pixels in the image file. Adobe PDF compression uses bicubic downsampling ranging from 100 to 1200 pixels per inch. The downsampling has a disadvantage that it deletes information from the file. Hence a better option is to use the Zip algorithm. It is absolutely loss less, i.e. no data is lost during compression. Apart from the above, simple steps such as unembedding fonts wherever possible, using PDF optimizer and most importantly using the Save As command instead of Save helps in reducing the size of the PDF files.
Advantages of Compressed PDF Files
Compressed PDF files are really small in their size and hence are very efficient to work with. They are shrunk to almost 1/8th their original size. This makes them easier to upload, download, and transfer as mail attachments and also in their storage as they occupy very less space now. The quality is maintained irrespective of how many pixels have been reduced. Hence one can store his/her files for a very long time without worrying about its efficiency as they are as good as the original when decompressed.