Sure can! knitCompanion can be used for free with all your knitting PDFs, using the built in QuickStart. You can also use kCDesigns with the free app. There are 5 free kCDesigns included in the app and hundreds more available on Patternfish.
There are also in-app purchase options for advanced features:
- Setup provides advanced Tools for tracking.
- Magic Markers let you find, color, highlight, and count stitches in charts.
- The kCBundle provides both Setup and Magic Markers.