So, if you’re using internal links in your PDF, they are not going to be as effective as you think. Links in PDFs don’t get processed like links on webpages. They are not counted the same way in terms of passing authority through them. People who create PDFs don’t always know how to add this info. The click-through rate on a PDF in a SERP is generally low anyway, due to weird SERP formatting. If you are publishing PDFs, you need to check this. Being not very descriptive, you can expect the click-through rate to suffer. For example, if there is no title tag, Google will pull the actual file name. The lack of metadata means that these documents usually look inferior to search engines. Yes, the PDF will probably be indexed, but its SEO performance will be substandard. You can use Adobe Acrobat to map some of that metadata, but most people skip this step before publishing the PDF on the web. Most PDFs lack the proper metadata for which Google looks. Saving a text editor or slid presentation as a PDG file doesn’t automatically add the correct document properties.

Here are some common issues and mistakes content producers experience with PDFs: If the PDFs are scanned images of type writer written documents (or obvious photos of printouts) rather than editable text you can use the Optical Characte Recognition (OCR) scan in the software to get the text electronically recognized ready for searching.Although you can optimize PDF files for Search, you're better off not. Other PDF writers should let you do the same.

In Adobe Acrobat - full version not the reader - you can set the properties and keywords for each file. may also provide more information since they are the creators of Adobe Acrobat which creates pdf files.

This brings up the Advanced Search box in google with the website already set to and the type of file set to pdf. Google also provide a Custom Search Engine that involves a small amount of code being added to the company website it's pretty simple to do. Google also lets you create a search for a singe website only, you can create a hyperlink (link) in a document which would bring up a search, eg

Google search for pdf files