I normally would recommend Adobe -InDesign/Acro Pro for these types of jobs. If you're looking for a free solution you should consider the following: Used LibreOffice which works well and your clients can download the programme, tinker with your design, then export as PDF. Works well with with a printable solution which can be attached to email. The other one that I have used a few years ago was AbleWord but this is aimed at Word users but as an all round PDF editor it will import all PDF's but maybe a pig to edit and might not quite have the same look as the original PDF.