How do I re-edit an existing PDF?

I had a document which I had saved after editing, I needed to make further alterations so I opened it but could not re-edit it. I later found that I needed to open the Adobe file and find where the saved file was and then  edit it again. Surely simple to understand the original question!

My second question was to ask how I can cancel the programme after the first month but I have had no reply, The method shewn on the Adobe website does not work.

I don't know what you mean by "re-edit"; using Acrobat you should be able to edit a PDF as often as you want.