Hi there,
There's a way to make all objects visible in form within designer, but no easy way to put them back hidden if the form is already made with hidden fields. If you go in XML source code and use the (CTRL + H) shortcut to find and change specific strings you can look for
Therefore, if you would like to have an easy PDF to modify within designer without having to find all the hidden objects in the form, you can keep all of them 'visible' and use the calculate event of subforms to calculate what object should be hidden or visible within that subform or the subform itself. This may be a lot of work when modifying a PDF which does not work this way, but afterwards it is very useful when the PDF needs to modified.
I hope this will help you!