Reduce Your PDF File Sizes

via pdfzone.com

How To: The main factors affecting the size of a PDF are image resolution, image type, fonts and how they're embedded, PDF version and the level of compression.


Here's a familiar problem: You've slaved away creating a comprehensive PDF document, and it's got everything from an index and bookmarks to gorgeous graphics and interactive forms.

There's just one snag: The file size is huge.

Most PDF users can tell you, the main factors affecting the size of a PDF are image resolution, image type (bitmap or vector), fonts and how they're embedded, PDF version and the level of compression.

If you're comfortable manipulating these elements in a PDF, you're off to a good start.

Below are a few tips to help you whip your heavyweights into bantam class performers.

Use the Save As Command
This is Adobe's No. 1 suggestion for reducing the sizes of your PDFs. When you make changes to your PDF, select Save As to overwrite the entire PDF. Otherwise, if you just click Save, changes are appended to your file, and you'll notice a slow and steady accretion of kilobytes.

Named Destinations: Use 'em or Lose 'em
Named destinations are markers that identify locations in a PDF file. Many PDF authors use named destinations for one document when they plan to link a second PDF file to a specific point in the first doc. (It's actually possible to deep link to a PDF file without named destinations. See this article for more info.) Unfortunately, every ten or so named destinations account for 1KB of file size. So if you don't need em, don't use em.

Use the PDF Optimizer
By selecting Advanced > PDF Optimizer > Audit Space Usage, you can find out which elements in your PDF (fonts? images?) are taking up the most space and make changes accordingly.

Manage your graphics
Graphics are always a big problem when optimizing a PDF for size. First and foremost, use vector-based graphics whenever possible. Vector-based graphics scale perfectly, look better and take up less space than their GIF counterparts.

If you have to insert a graphic as a bitmap, prepare it for maximum compression and minimum dimensions. Don't compress the graphic beforehand, because distilling them in the PDF may cause the creation of noticeable artifacts in the image.

To tinker with the image compression quality to size ratios, select Advanced > PDF Optimizer, and on the images tab select compression options for color, grayscale, and monochrome images. Or, select Enable Adaptive Compression and drag the slider to balance file size and quality.

Manage Your Color
If you're making a PDF for the Web and/or if you're not concerned about printing colors, use the RGB color space. RGB has one less data channel than CMYK, so your files will be that much smaller.

Minimize Fonts
Fonts take up a lot of space. If possible, don't embed your fonts. But if your document requires a certain look (and most do), keep the number of fonts to a minimum. Using subsetted fonts that only include the glyphs actually used will go a long way toward minimizing font size bloat.

Watch out for version bloat
Acrobat 5 (PDF version 1.4) introduced JBIG2 (Joint Bilevel Image Experts Group) compression, which is superior to the CCITT or Zip algorithms that previous versions used when compressing scanned monochromatic copy. Most PDF users have made the switch to newer versions of Acrobat, but if you're still using an old copy, it may be time to make the switch.