Something must have broken with this feature. I will investigate and let you know what I find. Sorry for the inconvenience.
UPDATE:
I appear to be checking for the matching .mp3 in the storage location instead of the in the original source directory (which doesn't make any sense). This is why it's not working. It currently will only work for people who have unchecked "Manage My Files" in the storage settings. I will get this fixed in the next update.
It also works in the song editor. If you tap "New" on the main library screen with the Songs or Recent tabs selected, then tap the folder icon, then select the PDF, it will find the matching audio file correctly.
UPDATE:
I appear to be checking for the matching .mp3 in the storage location instead of the in the original source directory (which doesn't make any sense). This is why it's not working. It currently will only work for people who have unchecked "Manage My Files" in the storage settings. I will get this fixed in the next update.
It also works in the song editor. If you tap "New" on the main library screen with the Songs or Recent tabs selected, then tap the folder icon, then select the PDF, it will find the matching audio file correctly.