Compression is the process of reducing the size of a file for quick transmission of data. Compressing the files before sending them through e-mail can save a lot of time, money and storage space. The widely used format for transmission of files is PDF. PDF files are usually large and you will need to compress PDF files to reduce its size.
To compress PDF file, different algorithms can be used. Some of the compression algorithms are,
FLATE (ZIP, in PDF 1.2)
JPEG and JPEG2000 (PDF version 1.5)
JBIG2 compression (PDF version 1.4)
RLE (Run Length Encoding)
The compression of the text in the PDF is done by removing unwanted spaces and characters in the file. The main process of reduction in size is carried out during image compression. The image compression is mainly divided into two types; lossy compression and lossless compression. In lossy compression the compression ratio of the file will be higher than lossless but a small decrement in the quality of the image can be observed in the image. This loss in quality cannot be observed in lossless but it has a smaller compression ratio.
Some common techniques can be used to compress PDF files. Minimizing the font and reducing the number of embedded fonts in the file can reduce the size of the file. PDF Optimizer can be used to compress a PDF file. Grayscale can be utilized if colors are not required in the PDF file. To get a decent quality of the image in the PDF file after compression, the image inserted in the file before any type of compression should be of high quality. Using Save As option instead of Save, while saving the document, can also help in compression. Saving or overwriting the compressed file on an existing file will remove unused elements in the file and thus reduce the file size.
Some plug-ins can be used to compress PDF file. Some PDF optimizing software and file reduction software can also be used to compress PDF file size.