I was playing around with my PD 10 today. How do add a custom font to a title:
Go to "Title"
Click on "Add Custom Title" in bar above the listed text templates.
Create your custom title template using the downloaded font.
Add title to movie/project.
Click on title once in title bar in your timeline.
Right-click "Edit title"
Go to "font"
Replace the default font with your downloaded font.
Click save at bottom of editor.
That should work! Worked for me with all my downloaded fonts!