Word Doc to PDF with fields to be typed in and saved .

We have a 14 page form document that is written in MS Word. The document is a form for people to fill in with a great amount of detail. We want the form made in to a format that we can email ??" PDF ? We want the people to be able to type the information in and tab between areas. They need to be able to save the document , then have the customer email it back to us. ? When the document requires updating we would like to be able to email the completed form back to the customer and they then make changes.? The changes should be in a different colour so we can see clearly what is the new text, additions and changes without having to go through the entire document. ? We also need to be able to write additional information on to the form.? ? The header on the form is also rather large and will have to be compressed or redesigned.