Compressing PDF with Algorithms
A PDF compressor works based on certain algorithms. Some programs have an algorithm that works well with screen shots and simple images. Repeated patterns work well with these programs as well, such as black and white images. Some methods are lossless, meaning they do not remove any data to decrease file size. You will keep image quality and original information within the file itself. If you combine some algorithm programs, data can be lost. If you use a 4 bit style compression with 4 bit images and an 8 bit style with 4 or 8 bit images this method is 100% lossless. You must be careful of these combinations. If you use a 4 bit combination with 8 bit data, information can be lost.
Compressing PDF to Lossy Styles
A PDF compressor can have a lossy compression algorithm. It can be compressed by a factor of 10 or more. It is best used to reduce the file size of natural, photographic images. This is done as much as possible without affecting the quality of the image. Some programs are great for continuous-tone photographs that contain a large amount of detail. Many of these files cannot be reproduced on screen or in print. You have many choices of program options from maximum quality to minimum quality. At one end of the extreme, you cannot tell that the file has been compressed. At the other end, images may become almost pixel like. It is very important that you know what is involved with your PDF files so that you can use the right PDF program to fit your needs. You don't want to over or under compress your files.
Compressing PDF with a Flate Method
Flate methods are very popular when using a PDF compressor. This form of variable length compression includes special adaptive coding. Many flate programs have a compression ratio of approximately 50%.