Good Morning,
That's a great question! You have several options. Here's what I've done with this situation.
Disable the file overlay and file preview in Canvas for that file. Why? Because DocViewer, the Canvas utility that enables the preview, just won't let students type in the preview into those form fields. Next, provide instructions to students on how to save the PDF after they fill in the form fields. Otherwise, their data won't transfer when they upload it. Finally, it's not directly applicable, but make sure your PDF is accessible, including ToolTips on all those form fields to make sure all students can use it.
You may also want to consider using a OneDrive or Google Assignments assignment if you want to leverage cloud storage, but that's not required. There are ways to turn a Microsoft Word document into a form-fillable document. Let me know if you'd like more info on that.
I hope this helps!
Nathan