Let’s start with a link to the official support article! https://wordpress.com/support/embed-a-pdf-file/
It’s very easy to upload a PDF onto a page or a post. But once again, size matters … PDFs can be large, like photos. The larger your PDF, the longer your page takes to load, and the more storage it uses up on your hosting account. So it’s really important to try to remember to compress PDFs before you upload them.
Step 1 – Compress your PDF
You can easily compress your PDF by using this site https://smallpdf.com/compress-pdf
As an aside, Smallpdf.com is a fantastic site which does a lot more than compress PDFs … check it out. They also have a generous free tier (these links are not affiliated and I receive nothing for making this recommendation)
Simply drag your file onto the box, or upload from file manager. Select ‘Basic Compression’ and then download the compressed file.
Tip: you only get 2 free tasks per day, but you can easily work around this by using a private / incognito tab and then opening a new one after 2 compressions (or clear your site cookies for the same effect).
Step 2 – Embed your PDF
Now you have your file, you can easily embed it! Just add a ‘file’ block to the page, and then click upload to upload your PDF. Once added you’ll get a PDF viewer, with a download button added automatically for you