Building a PDF library the right way for speed.

WordPress Mobile Speed


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We’ve done library sections on websites before. They are popular (meaning they are visited from search engines). But success is contingent on several things for SEO (search engine optimization). These things are details improving what is called findability.

Findability means visitors can easily find what they are searching for on the site. And it also means being able to find relevant information from offsite (from search engine listings – like Google).

So why this tutorial?

The newsletters that are frequently on websites are not findable. They are invisible. In fact, they aren’t listed on Google.

Our goal is to get every single page and document listed on Google. WordPress will handle most of that problem. But other things can help.

Why are some PDFs not listed? They aren’t MACHINE-READABLE. They are image files. If you try and highlight (select) the body text with the cursor, it can’t be done. That means search engines can’t read the text either. The files haven’t been saved with embedded text.

Do PDFs rank well when they are machine readable? The answer is “yes.” Engines can crawl them just as well and fast as regular old web pages. The PDFs rank sometimes even better than HTML web pages. Search Engines are looking for credible content. And PDFs have high credibility. They take longer to prepare. They are less disposable. They have a longer shelf life.

A library directory is a good thing. But library production requires a little more tender-loving care.

Here’s what that means:

1. Save a PDF with embedded text.

2. Optimize the PDF for fast download.
There are various ways to automate optimization (file size reduction) with plugin or online tools. PRESS quality PDFs (300dpi) are too fat for downloading. Even PRINT quality (150dpi) can be marginally heavy. SCREEN quality (72dpi) can ruin images. So some experimenting is required. Visitors won’t tolerate slow downloads. And heavy PDFs open and scroll too slow. Fat PDFs say, “We don’t care.”

3. Build a thumbnail image for navigation.
We can’t use the regular WordPress thumbnail function on PDFs. It works on JPEGs and PNG files. So we build the thumbnail by opening the PDF in an image editing desktop program. And then just save the cover page as a JPEG image file. We then upload that to the WordPress image library. This will become the link to the actual PDF.

4. Add the thumbnail image to the library page.
Editorialize the image link. This means descriptive text is added that tells what sort of content is in the PDF and why the visitor would benefit from downloading it. (Search engines read this stuff, too). This text is called information scent. It cues the reader that they are on the right track. The text should state that the download is free. Also, the file size, dimensions, color, and page count should be stated. This information helps them know how long they will wait when they click the link. Visitors don’t like surprises and are apprehensive about pressing any “mystery buttons.” Consider this advertising the PDF.

So there are a few hoops to jump through when preparing a library. Based on our experience, do we think the trouble is worth it? Absolutely. Library sections are popular with both people – and engines. They are a good draw. Some people will drop into the site right on the library page – bypassing all other pages.

We also encourage harvesting content from the brochures and make HTML entries to the blog. This redundancy is perfectly acceptable because people like information delivered in different ways. They have a choice.

Just a note: These kinds of pages with many thumbnails (also called catalog pages) benefit from a WordPress lazy-load plugin to keep load time fast. One we recommend is Rocket Lazy Load. Lazy loading defers loading images in long web pages. Images outside of the browser viewport (below the fold) are not loaded until the user scrolls to them.

For more about automated PDF optimization, read our article: Polite PDF Downloads


Steve Teare
performance engineer
October 2021


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