- Create (or edit doc settings) to make your canvas auto-resizing:

- Create an Omnigraffle iPhone template to copy and paste out the phone:

- Make each view and the app map their own canvas.
- When you are done and want to create a pdf, manually select the canvases that you want to put on different pages of a pdf by command-clicking on all the canvases you want to export:

- Go to File > Export:

- Change the format to PDF vector image:

- Push save
Please let me know if you have any issues with this or any other parts of the Omnigraffle interface.