PDFs displayed using the PDF Embed API are not indexed and won’t appear in search engine results by default since the API doesn’t store a direct reference of the PDF URL in the DOM. In order to index the PDF so that text appears in a search result, the URL of the PDF must be available in the website DOM. Search engine bots start by reading the website content and navigate all the links in the DOM.
Search engine indexing and optimisation of any website can only be controlled by the website developers. One approach which enables PDF indexing via the PDF Embed API involves using sitemaps.
A sitemap is a file which contains information about the pages and other files on the website and the relationships between them. A sitemap tells search engines which pages and files are important in the website and also provides valuable information about those files. It helps search engines find the content, crawl the website more efficiently, and index the content.
In order to enable indexing of PDF files displayed using PDF Embed API, website developers can add the PDF URL to the sitemap. For example, so add an URL to an XML sitemap of a website:
<url>
<loc>https://example.com/PDFs/example.pdf</loc>
</url>
Every <url> tag must contain a <loc> tag which would contain the URL of the PDF. You can have multiple <url> tags to add URLs of different PDF files.
The search engines will crawl these links found in the sitemap and index the PDF content accordingly.
For developers who don’t wish to use sitemaps, there are alternative approaches to enable search engine PDF indexing. The URL of the PDF file should already be available in the website to enable indexing. Website developers can trap the click of the PDF link and open the PDF using PDF Embed API. Developers can create as many user experiences as possible with this approach using the different configurations provided by PDF Embed API.
Here are some of the ways to implement this:
Auto-click on the PDF link after the webpage loads completely and open the PDF in the desired embed mode.
Create a separate webpage to display the PDFs in full window embed mode by passing the PDF reference.
Open the PDF in line within the context of the webpage.
Open the PDF on top of the webpage using the lightbox embed mode provided by PDF Embed API.
Find the working code samples here under /More Samples/Handle Search Engine Indexing/.
Note
These are only suggestions, and it is up to the website developer how they do the actual implementation depending on the design and structure of the website.