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The creation of documents using the “Portable Document Format” (PDF) developed by Adobe Systems in 1993 has become a ubiquitous format for document delivery over email and internet. PDF documents are often viewed on the internet as a webpage using a browser-based PDF viewer that shows the document when the visitor clicks on the link to the document.
Search engines have evolved to develop the ability to crawl and index these PDF documents in a similar way as with regular HTML-based webpages. In this post, we’ll cover how to optimize your PDFs for search.
What Search Engines Index on PDFs:
Search engines catalog pages found on the internet by using special programs called spiders that “crawl” websites and logically group information by the content they find. This is a process called indexing and can be likened to a library card catalog where the relevant information is stored for retrieval.
In the case of the search engines, this index is a complex repository allowing multiple ways to access the information via a search query. The information that the crawler sees in a webpage is pulled from both the content on the page and the “meta data” located within the page code. This meta data includes the page title, page description, and many more content attributes. We can optimize these areas of meta data to improve the search relevance for important or popular search term.
Just like with a traditional webpage, there is a function within Adobe Acrobat to add relevant information that can improve the “searchability” of a PDF document. The search engines look for the same attributes in a PDF file that they look for in a webpage. These attributes include:
- Document or file name
- Document title
- Authors/Owners (if appropriate)
- Document subject (similar to meta description)
- Relevant keywords
This important document information is located in the document properties under the “description” tab. The example below, taken from the Adobe Acrobat XI quick-start guide on the Adobe website, shows the fields that contain this information:
The document or file name is often left up to the discretion of the author. The format of the file name can be as varied and as individual and the author’s personal naming system and can include a recognizable nomenclature or naming structure.
This document has some clearly visible traits in the file name “adobe-acrobat-xi-pdf-redaction-remove-visible-data-from-pdf-files-tutorial.pdf”. The image below shows how the file name shows up in the search engine result. The author did a nice job of clarifying the Adobe product name in the title, making it more relevant for the searcher.
The image above shows the Google search result for this document. The main link in blue has been pulled directly from the document title. This provides PDF authors a significant opportunity to provide a very relevant and descriptive search title. The goal of creating a compelling title is to leverage the search engine algorithm, which looks to return the most relevant result for a given search. In addition, the use of targeted keywords in the title is essential just as it is with a webpage. The keywords in this title include the “brand” terms PDF files and Acrobat XI along with the “non-brand” terms redaction and sanitization.
The document subject in a PDF document plays the same role as the Meta description in a webpage. The part of the search engine result that describes the content of the result is called the “snippet” and is usually right below the main link. The search engines will first try to pull the content for the snippet from the first paragraph or 250 words of the target page; if that is not the most relevant description, the search engine will use the meta description or the document description in the case of a PDF document. The example above shows that the first part of the snippet was pulled from keyword occurrences at the start of the document.
The keywords field in the document properties of a PDF document provides a location for a list of important keywords found within the document. This helps the search engines by providing additional data for scoring the pages for relevant keywords not located in the title or subject fields. Some rules of thumb include:
– Try to always use the same field for similar information. For example, don’t add an important term to the Subject option for some documents and to the Keywords option for others.
– Use a single, consistent term for the same information. For example, don’t use biology for some documents and life sciences for others.
– Another option is to use the Subject or Keywords option, either alone or together, to categorize documents by type. For example, you might use status report as a Subject entry and monthly or weekly as a Keywords entry for a single document.
The document author is an important field for grouping documents by the team or group that was responsible for their creation. An example would include a hiring policy document, which would have the “Human Resources” department in the Author field. This could also be used to demonstrate the core competency of a particular thought leader within the organization.
The importance of natural search is driving the need to provide the best possible results for the searcher. This effort includes providing better search results, better user experience, and improved asset management. In the end, this expanded use of meta data simply tells more about the many documents located on websites and making these PDFs easier to find and manage through search.