Only include things that you actually refer to in your PIP. For example, say you're talking about about a particular problem you encountered with your questionnaires, you might want to include a copy of the questionnaire in the appendix and make a note of that in your central material :
"I found that the responses to question three of my questionnaire were not answered properly, which may have hindered the validity of my research (see Appendix, questionnaire one, question three). I believe this was because.... blah blah blah"