Success!
 

Thanks again for everyone's help; Jh for keeping the mind active.
G, I am using iFiles and iBooks within their limits. iFiles is good for capturing text, cut and paste, and allows direct PDF output via 'send a copy' - Acrobat . iBooks enables PDF copy of web pages, then email to self for use in Acrobat.

le Pingouin, yessss !
The File Explorer App has the option to add (+) an external location.
Western Digital was in the menu - the hard drive which was connected as a 'NAS'. However, by choosing the NAS option and thence via the BT Hub to the usb1 option, all files on the hard drive can be accessed (no login or system address required). So far some files can be saved back to the hard drive from the iPad via iFiles, Acrobat, and PowerPoint.

The add location option appears to be restricted to a one off use, or limited locations where many are provided - a range of NAS's. An upgrade to the pro version offers unlimited access . So far so good, even if my set up is a time limited system, the pro option provides many opportunities.

Didn't notice it was a limited version of a "pro" app. Glad it's working for you.

FWIW I Googled "file access ipad nas" (without the quotes) and that was the top result - you might something useful further down the results or some hints.

That is the app I'm using. I have the pro version and it is working like a charm with my network drive. It remembers the network name of the drive as 'recently used' on the first screen. One tap on that and I'm able to browse the entire drive, open files, etcetera.

A downside of the Apple system is that you can open a document this way, letting FileExplorer open Pages for a Word file for example, but it may be difficult to get a changed file back to the network drive (I have never tried that). Once a file is in Pages though, it can be automatically backed up in iCloud (depending on your settings) so that the file remains available both in the cloud and on your iPad. You'll have to let the idea of storing files in one place (on the network drive) go if you want to edit them as well.