Picture this; the deadline is edging closer and you have to send a copy of an image heavy article to a colleague via email. You decide to scan the document in and output the images into a PDF, then attach that PDF to an email. You hit send, but the mail server spits back “file size too large”. What can you do, the document is all images!?

Frequent PDF supporter will advise you to keep as much of a PDF in plain text, use vector graphics instead of images and never embed fonts. These are all good suggestions, but in our case none help. The PDF could be Zipped, but that doesn’t guarantee a significant drop in file size.

It’s best to optimize the images before converting them to PDF, but if you don’t have access to photo editing software you’re not completely out of luck. There are at least two ways to optimize an existing PDF’s file size, smaller.

First open up the PDF in Adobe Acrobat (note, Acrobat Reader will not work), then go to File > Reduce File Size > choose the lowest Adobe Version Compatibility option (say Adobe 4.0) and click OK. In our tests this brought a 6 page PDF of all images from 18MB to 2MB. The second method is tucked away under the Advanced tab > PDF Optimizer. By clicking the “Audit Space Usage” you can see exactly what components of your PDF occupy the most space, and optimize strategically. In our example it’s all images, so the only option is “Scanned Pages.”

Click on the “Scanned Pages” option and move the “optimize compression of page regions…” slider all the way to “Small size.” This is an extreme example that sacrifices image quality, but reduces PDF size the most aggressively. The best choice is to find the quality level you’re comfortable with. If image quality is too degraded, move the slider a notch or two towards the higher end of the scale.

For our 18MB PDF, the Low end of the scale reduced file size to 672KB, middle to 1.2MB and High to 11.5MB. A 1.2MB attachment is certainly easier to email than a bloated 18MB PDF!