First, why would anyone want to search engine optimize their PDF files? Well, if you had an eBook, brochure, product description or technical document in PDF format, you may wish to optimize these to pick up some extra search engine traffic.
Can search engines read PDF files?
Yes, most of major search engines now can read basic contents of PDF files, though getting these pages to rank as well as HTML files is still questionable.
How is it supposed to work?
This is how workflow is supposed to work. Create your file in MS Word, or in a draw or page layout program that later can be distilled into a PDF (with some applications you will have to create an EPS file first and then distill it and with other applications, you can distill right out of apps). If you are using a program such as MS Word, be mindful to apply H1, H2, H3 tags where necessary and optimize body text as you would an HTML file.
When you are finished, distill file. Bring this file into full version of Adobe Acrobat 6 for editing. Plug in appropriate content, post PDF on your website and let search engine robots index file.
How do I plug in appropriate content?
In Adobe Acrobat 6 there are two places to input content into a PDF file. The first place is under File / Document Properties and second place is under Advanced / Document Metadata. Under File / Document Properties there are several menus but most relevant for our purposes is Description menu. Under Description menu, there are fields for Title, Author, Subject and Keywords.
Now to confuse matters more, let’s go over to Advanced / Document Metadata menu. There are a couple of choices here, but let’s once again look at Description menu. Under this Description menu, there are fields for Title, Author, Description, Description Writer, Keywords, Copyright State, Copyright Notice and Copyright Info URL.
How does PDF store data?
With duplicate fields, it is important to find out how data is stored so that we may make some educated guesses as to how search engines read this data. I performed a few small experiments and here is what I have found. The Title and Author fields seem to be linked to each other because when you change one and check on other you will see it too has changed. Also, Subject field of Document Properties menu seems to be linked to Description field of Document Metadata menu for same reasons. The Keyword fields, however, are not linked. Separate sets of keywords can be added to both fields. When file is saved, both sets of keywords are stored in PDF file.
Which set of keywords is correct then?
Adobe stores its metadata in XML format. Opening PDF file in Notepad, it appears that Keyword field under Document Properties is one that search engines will use (this hasn’t been proven, yet though). The keywords input into this field appear in PDF as we have come to expect, separated by commas, like this: Keywords(movies, cinemas, matinees, theatres, popcorn).