[Zubersoft]

Long press a song to select it on the library screen, then tap "Edit Song" in the action bar. Go to the Files tab, tap the three dots next to the file in the list and tap "Image Correction". MobileSheets is going to need to first render an image for every page in the entire PDF. It then will process every one of those rendered pages to apply the image correction to it. Just be aware that if you do this with a 274 page PDF, for example, it's going to take an extremely long time to process every page. 

Mike