You can only map similar fields to each other if they have the same type.
Merge webform fields
When you upload a new PDF, Anvil will automatically add all the identifiable fields to your webform to get you started. Often, PDFs will ask for the same information more than once and Anvil will insert a webform field for each instance. Combine fields to collect the necessary information once and map it to as many PDF fields as required. If you would like to delete redundant webform fields and also remove their PDF mapping, remove the webform field instead.