Thanks for your help.
Here’s a solution for iPad iOS:
Download the .zip from PianoBook using a Mac computer.
Do not extract the zip, in stead edit the suffix to .dslibrary.
Copy the file using a USB connection via iTunes file transfer. (samples will turn up in decent sampler folder.)
Do not attempt to Airdrop the .dslibrary file, they seem to disappear.
If necessary leave the .dslibrary files on the Mac for use by the Mac version of DecentSampler.