This is easy peasy, and you don’t need any plugin to do this: just use the WordPress editor’s built-in FILE block to upload and insert the PDF file!
(This assumes you’re using the default “block” editor that comes with WordPress. If you’re using a 3rd-party editor or page builder plugin, you’ll have to contact the developer of that particular plugin for help.)
First, click the PLUS (+
) sign, type “File”, and click the “File” block to insert it.
Next, click UPLOAD to locate the PDF file on your computer and upload it to your website. Depending on the size of the PDF file and your internet speed, it might take a whole for the file to be fully uploaded to your website and inserted into the post.
After the file is fully uploaded and inserted into your post/page, you should now see a screenshot like below, with various controls on the right. You can toggle on/off the document preview, download button, etc.
I hope that helps.
If something is still not clear or you need further help, feel free to ask any follow-on question!