One app for your iPad or iPhone
PadLink Go controls your classroom PC and prepares lessons anywhere, even with no internet. It opens on your boards; tap Control the PC when you're ready (or switch on Open on this PC by itself under Connect to your PC). In the control screen, Boards at the top left comes back here: the PC stays paired, so Control the PC connects again without Allow.
Open it from the Home Screen
In Safari, tap Share → Add to Home Screen, and always open PadLink Go from there. It then works offline, and your boards are kept safe. (Boards made in a Safari tab are kept apart, and Safari may clear them after a week without use.)
Making a board
New board, then the same tools as on the PC: pens, highlighter, shapes, text, math, sticky notes, pages and backgrounds. On an iPad, draw with Apple Pencil; drag with a finger to move the page and pinch to zoom (with Select, a finger on what's selected moves or resizes it). The Fingers choice in the Control the PC screen applies here too (phones default to using a finger like the Pencil). Add puts in a photo, a screenshot (from Photos), a picture or PDF worksheet from Files (choose its pages), or takes a photo with the camera. Add → Google Drive brings in a picture, PDF, or Google Slides, Docs or Sheets (as pages you pick): it needs the internet, but not the PC. The picture button (beside the bin) saves the page to Photos or Files. Everything saves itself. ✕ goes back to your boards.
Sending to your PC
Connect once: tap Connect to your PC at the top, scan the QR code in PadLink's window on the PC, and click Allow there. Use Connect to another PC to add another without forgetting this one; your paired PCs stay in the connection panel so you can switch between them. Sent ✓ is shown for the PC you're using now. Then Send to PC: one board from its ⋯ menu, or all of them at the top. The PC needs PadLink running with Remote mode on.
Boards show Sent ✓ once the PC has them, and Changed since sent after you change them. Sending again updates the PC's copy; if it was changed on the PC too, the new one arrives as a copy, so nothing is lost. Open on the PC (⋯ menu) sends a board and opens it on the whiteboard. From the PC keeps a copy of one of the PC's boards here.
Keeping boards safe
Boards are kept only on this device, in PadLink Go's own storage, until you send them. Deleting PadLink Go from the Home Screen deletes them. For a backup or to move a board, use Share as a file (⋯ menu) to Files, Google Drive or AirDrop; Open a board file brings one back, here or on the PC.
Privacy
PadLink Go has no accounts, ads or tracking. Your boards go only to a PC you paired, and that PC can only receive boards from it.