When you open an Editable-text Party Printable file in Adobe Reader, you should see all text fields highlighted in pale-blue rectangles.
If the text fields are not highlighted click on: “Edit” → “Preferences”.
In the window that opens choose the category “Forms” and check the box that says: “Show border hover color for fields”.
(Click on the image to enlarge or see a larger image here).
If you want to remove the highlighting of the text fields (for instance when taking a screenshot of your invitations to send by email) make sure the box is unchecked!