Each job's submittals and PDFs (sent from the office or added here). Open one to read it; pinch to zoom. Use Move to Submittals / Move to PDFs to file one in the other group. Files you add on this iPad go to the PC when it is connected.

Ask the office to apply a submittal to a drawing, for example the proposed control lines on a contractor's sheet. Pick the submittal, the page, the drawing and what to apply, add a note if it helps, and send. Save it as a draft to finish later. Once sent it moves through In progress to Drawing ready, and the blocks below show where each request is. A request made without a connection goes to the PC when you are back on.

Line a PDF, DXF or DWG up on one of the job's drawings: import it, pick the drawing, then tap the same place on it and on the drawing, at least twice (three or more checks it). A DXF or DWG is drawn as a sheet on the PC at its own scale, keeping its layers (a DWG is converted to DXF on the PC first). Save it and it is kept under Aligned PDFs in Drawings, where it lays over the drawings like any other.