(Edit 6/14/13: CS 6 allows you to create your form fields directly in InDesign, so this finally resolves the need for cumbersome workflows such as the one described below. If you are using CS6 or newer, consider building your form in InDesign so that when you export the PDF all fields are included, and you don’t have to edit them in Acrobat at all. To get started making forms in InDesign, go to Window: Interactive: Buttons & Forms. Enjoy!)
Many people use Acrobat Professional to create fillable forms and other interactive documents for online use. In recent years Acrobats form creation features have improved and become more automated and easy to use. Although some Windows users have worked with the LiveCycle Designer application (included with Acrobat on Windows), the most common workflow is to use some other application, such as MS Word or InDesign to design the actual document, then converted it to PDF, open it in Acrobat Pro, and add form fields and other interactivity. However, form designers using this method are faced with a common dilemma: What if changes must be made to the original document?
Acrobat isn’t very good at editing documents. True, it has the Touchup Text and Touchup Object Tools, but these are good for only minor of edits, and only if you have all fonts used in the PDF installed on your system. Usually changes must be made in the source document and a new PDF exported. But then do you have to re-create all the form fields?
Thankfully, no. You don’t even have to copy the interactive elements over to the new file. The best way to do this is to import the new PDF pages into your existing PDF form using the Replace Pages option.
“Replace Pages” Preserves Items Created in Acrobat
The heading says it all. Feel free to open up your source document in MS Word, InDesign, or whatever application you’re using, edit it, and export your new PDF (but don’t overwrite your form!). If the new PDF opens automatically, close it. Now, go to Acrobat Pro and open your old PDF containing the interactive elements that needs to be updated with this new content. Open the pages panel (usually on the left side of the screen), right-click on the page(s) you want to replace, and choose “Replace Pages.” Select the appropriate page range from the dialog and choose OK.
If the changes you made caused reflow in the document, you’ll notice the items created in Acrobat need to be readjusted. Since Acrobat’s interface has changed radically over the last couple versions I’ll refrain from writing instructions here; it’s not difficult, and usually involves using the form editing tools to realign your form fields and other items.
How (Why) It Works
PDF contents are arranged in layers, analogous to other Adobe applications. When you create comments, for example, they reside on the topmost layer, which is reserved for markup. Form fields and buttons are a special layer as well. The page content layer is down below these special layers. When replacing pages, Acrobat swaps out the page content layer, leaving the other layers intact.