- KnitCompanion is a complex but extremely powerful app to take PDF patterns and turn them into very efficient, effective digital patterns. You can designate specific steps, walk through steps and charts with voice control, extensively reformat a pattern, etc. I use this for all moderately complex knitting.
- TinCanKnits is a pair of pattern designers who have recently released an app for their own patterns that customizes the pattern (showing only your size, changing chart colors to match your yarn, etc.)
- CustomFit by Amy Herzog is a tool with a collection of sweater designs that can be fully customized to your own gauge, measurements, design preferences, etc.
- There are a number of calculators out there for sock knitting (how many stitches/rows for heel flap, gusset calculations, etc.).