Telale OP, if you’re gonna try recovery, don’t download or install anything to your Mac’s internal drive right now. Every new file you download might “replace” your PDF if it’s still somewhere on the drive. Just “invisible” to the system because it was deleted.
If the file’s that important, you might wanna play it safe and before you download anything else, switch the download location in Chrome:
Chrome Settings > Downloads > Change
Then pick a folder on an external drive or USB drive (if you have it).
Here’s how it looks in my Chrome browser. 
While you’re there, you can also turn on the option for Chrome to ask where to save each file before downloading. That way, you’ll always know exactly where stuff ends up.
