Hello Geoff Irby, Welcome to the Microsoft Community. I understand that you are currently experiencing link failure when editing your workbook on your iPad, and based on what you've provided, if these are linked text inside your document, and since they look like filenames, the first thing I'd want to confirm is whether the links inside this document are pointing to a file or a web page?
If they point to files, since the iPad and your PC have different file systems, these links really won't work on your iPad, even if you add the linked files to your iPad.
And if those links are pointing to web pages, then I'd like to confirm what kind of error message you're experiencing, and different error messages can point to different types of problems. Until I hear back from you, you can click on those links, select Edit, refill them with their corresponding link URLs, and then save the file to try again.
Hope this helps! Best RegardsEliac.S - MSFT | Microsoft Community Support Specialist