You can insert a PDF into Google Slides by converting it into images or creating a link to the same. This post covers both methods in detail.

Note that the Save as PDF option can be accessed from the Print dialog window within a number of macOS apps, not just Preview. You can use it to create PDFs of web pages viewed in Safari, or Word ...

However, you can insert a PDF document in OneNote as a file attachment or printout image. You just have to use its insert feature to add a PDF document to your notes.

Outlook 2013 supports the inclusion of JPG, GIF, PNG and BMP image files directly in a signature. To add a PDF image, you must include it as a Web link.