| Why
optimize?
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 the search
engines read PDF files?
Yes, most of
the major search engines now can read the 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
the 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 the
apps). If you are using a program such as MS Word, be mindful
to apply the H1, H2, H3 tags where necessary and optimize
the body text as you would an HTML file.
When you are
finished, distill the file. Bring this file into the full
version of Adobe Acrobat 6 for editing. Plug in the appropriate
content, post the PDF on your website and let the search
engine robots index the file.
How do I
plug in the 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 the second place is under Advanced / Document
Metadata. Under File / Document Properties there
are several menus but the most relevant for our purposes
is the Description menu. Under the Description menu, there
are fields for Title, Author, Subject and Keywords.
Now to confuse
matters more, let’s go over to the Advanced / Document
Metadata menu. There are a couple of choices here, but let’s
once again look at the 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
the PDF store the data?
With duplicate
fields, it is important to find out how the data is stored
so that we may make some educated guesses as to how the
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 the other you will see it too has changed.
Also, the Subject field of the Document Properties menu
seems to be linked to the Description field of the Document
Metadata menu for the same reasons. The Keyword fields,
however, are not linked. Separate sets of keywords can be
added to both fields. When the file is saved, both sets
of keywords are stored in the PDF file.
Which set
of keywords is correct then?
Adobe stores
its metadata in XML format. Opening the PDF file in Notepad,
it appears that the Keyword field under Document Properties
is the one that the search engines will use (this hasn’t
been proven, yet though). The keywords input into this field
appear in the PDF as we have come to expect, separated by
commas, like this: Keywords(movies, cinemas, matinees, theatres,
popcorn).
The keywords
that were input into the Document Metadata menu appear as
a sort of list like this: <rdf:li>trees</rdf:li><rdf:li>wood</rdf:li><rdf:li>chips</rdf:li>
Of course, this
doesn’t mean anything really – it is how the search
engines read this that counts.
How does
it really work?
I’ve run
some preliminary tests (and by this I mean very preliminary)
and more testing will need to be completed to verify these
results, but here is what I have come up with so far. When
a PDF file was first opened in Acrobat 6 the Document Properties
or Document Metadata title and author fields were already
filled in with the file name and author’s initials
(information received from MS Word)
Without filling
in any extra data into the Document Properties or Document
Metadata menu, Google used the Title field information for
the title in the results and the description in the results
was acquired from the body copy. Yahoo!, in older PDF’s
use the largest text on the page as the title text. In regards
to more recently indexed PDF documents, however, Yahoo!
is using the Title field information as the title text in
the search results. At this writing, the description text
in the search engine results comes from the body text of
the PDF and not the Document Properties or Document Metadata
text.
Thinking I might
just get lucky (and hoping for quick results), I ran a few
optimized and non-optimized PDF’s through some of the
more popular search engine spider simulators on the web,
but these spiders did not handle the binary code very well.
None of them returned title or meta tag information and
the most popular keywords were snippets of binary code.
So, at this
point, does it really pay to optimize a PDF?
The simple answer
is, yes. The title tag and body copy can still be optimized
and the major search engines will index it accordingly.
As far as the Keywords and Description meta tags, well Google
ignores this in PDF’s just as it does in HTML documents
and Yahoo!, which does use the description tag, is only
half way to where it needs to be.
But Google and
Yahoo! aren’t the only two search engines / directories
around and with algorithms changing all the time, perhaps
someday soon either the SE’s will be able to fully
read a PDF file or Adobe will offer a patch that will make
PDF’s more SE-friendly. It’s only a matter of
time, my friend. Will you be ready?
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