I presume that's a dissertation compilation. If so, congratulations. They're two ways yo can go about (both tiresome):

1. Convert the PDF to MS Word: depending on the software you use, you risk losing your formatting. You can try Foxit Premium or Acrobat PDF editor.

2. Merge the files in MS Word before converting to PDF.

• Make sure each chapter you start on a 'new section' under page 'layout'. That way you will preserve the flow of your chapters.
• Format your Heading 1, 2, 3,...
• Insert your Table of Contents

Thanks Edmond, I will try to search Foxit Premium.