The main factors that affect the size of a PDF file are image resolution, image type (bitmap or vector), fonts and the way they are embedded, PDF version and the level of compression. It is challenging to reduce the document size when it contains index and bookmarks to dazzling graphics and interactive forms. However, few tips should be kept in mind while reducing the PDF file size.
Using the Save As Command- When changes have to be made to the PDF file, it is better to use the Save As option to overwrite the entire PDF file. Otherwise when the PDF is saved by clicking the Save option, changes are appended to the file, and there will be a slow and steady accretion of kilobytes.
Named Destinations-Named destinations are markers that identify locations in a PDF file. This option can be used when the user plans to link a second PDF file to a specific point in the first PDF document.
Using the PDF Optimizer- The user can find out which elements in the PDF (whether fonts or images) are taking up the most space and make changes accordingly by selecting the Advanced > PDF Optimizer > Audit Space Usage option.
Managing graphics-Graphics pose a greater challenge when optimizing a PDF for size. The first and foremost advice is to use vector-based graphics wherever possible. Vector-based graphics scale perfectly, look better and take up less space than their GIF counterparts. If the user prefers to insert a graphic as a bitmap, then the maximum compression and minimum dimensions option has to be considered. Care has to be taken not to compress the graphic beforehand because distilling them in the PDF may cause the creation of noticeable artifacts in the image.
Managing Color and Minimizing Fonts -If the PDF file is for the Web and it doesnt require much of color in-depth then the RGB color space can be used. RGB has one less data channel than CMYK, so that the PDF files can be made smaller. Fonts take up a lot of space. It is better to use minimum fonts than embedding them. Using subsetted fonts will help in minimizing font size bloat.