Where to submit ticket about printing PDF issue I was not able to print a password-protected PDF with Preview even though I have the password. 

But I'm able to print with Adobe Acrobat Reader

Where is Apple's bug tracker to submit issue?
File bugs at https://bugreport.apple.com

Start with https://developer.apple.com/programs/which-program/ and at the bottom of the page is a free option to start up a developer account (which will need an  AppleID) you want to use for bug reporting.

Lastly, check out QuickRadar and http://openradar.appspot.com/ if you want others to see your bug report.