...but this whole thing is getting to be a real mess. All we want is to have text control over the documents we have had designed for us.
This is the key point. Did you discuss this with your designer beforehand or did you spring this on them after the design work had been completed? It makes a huge difference in how the files
should be set up and determining who is responsible for this big "mess".
If I were to make a bet, I'd bet that you hired a designer to do some work for you and that
after the work was completed you decided to save some money and asked for the files so you could make changes to the text. If this is the case then it's not the designer's fault. They were hired to delivered a product and were free to use
whatever tool they preferred so long as it produced a satisfactory result.
Imagine the designer's dismay to hear that after all their hard work their client decides to take their files (which never "belonged" to the client in the first place) and make changes to them. Then the client starts putting demands on the designer, taking their billable time, because the client is having trouble converting the files. Are you paying for the time the designer is taking to help you through this? I certainly hope so.
If on the other hand, you had talked to the designer from the beginning and told them of your plans to make text updates to the design then many of these problems should have been avoidable. Fonts would have been chosen that were cross-platform compatible. Files would have been formatted in ways to make these updates easy. Style guidelines would have been developed so your design would remain consistent regardless of who was updating the text.
So which is it? Are you the client from Heck reaping your just rewards for not communicating with your designer? Or are you the victim of a "designer" who didn't know what they're doing and causing you unnecessary heartache?