The least expensive Adobe product that will allow you to do that is Acrobat Standard, though I'm still not sure exactly what you mean by "edit". I understand what filling out and saving means, but "edit" is more general and can mean a lot of different things. Also, sometimes documents that look like forms do not include actual interactive form fields, in which case you can use the Typewriter tool that's available with Acrobat to complete them. If the forms happen to have interactive form fields and are Reader-enabled, then you can use the free Adobe Reader to fill-in and save. Reader-enabled documents allow Reader to do things that it normally cannot, such as saving a filled-in form.
You can buy Acrobat directly from Adobe online or through one of their many resellers.
