A family of Microsoft word processing software products for creating web, email, and print documents.
Conversion from pdf, opening a pdf document for editing in Word often adds unneeded section breaks as a part of the conversion process. PDF format is looking at margin changes (which require section breaks) rather than Indent changes (which are paragraph formatting). This is true of converting from any non-Word format.
Try creating a new document, pasting your content as plain text, and doing formatting using styles.
The Importance of Styles in Microsoft Word
If you would like, save a sample document with the problem on OneDrive or DropBox and post a view or share link to it here.
Why a sample file is important for troubleshooting - - - - - - - and how to do it.
I or someone else will take a look at it and give you step-by-step pointers.