How do you filter a dropdown list based on user input. Say, the countries list. when the user types either "a" or "A" the dropdown list should list all country names starting with "A". Usage in standard PDF Form and not in Lifecycle Designer form. Thanks.
From my experience you can't do it with just the dropdown field alone. You need an extra (text) field to act as the "filter".
When the user enters something in that field you can use the validation event to change the items displayed in the dropdown.
I've actually created a (paid-for) tool that sets it all up for you, if you're interested. You can find it here: Custom-made Adobe Scripts: Acrobat -- Create Live Filtered List
Programming lists can be complicated. You can find lots of information and samples at these links: