So a quick update. In the spirit of “And now it works…”
After I posted this response, I went back to square one. I deleted my UiPath Sequence and tried again.
As per a suggestion from UiPath, I went into UiPath Explorer and clicked the gear icon at the top for “Frameworks.” I switched from Default to “UI Automation.” I then used the selectors suggested by the UI Explorer for my first selection overwriting the generic selector that my recording generated. It worked!
Then I started a new recording and the subsequent selections worked without having to use Explorer. The Selectors are using the unique IDX cntrl for each field.
So assuming this works, to automate populating a PDF, you would use a standard approach of 1) Read data from source into variables, (2) Use an Attach Window command followed by (3) Type Into Action and use the variable created in Step #1