Pages is not a Word clone, and as obvious as that may sound, Word uses hidden styling behind the text that it presents, and Word-specific styling is not 100% compatible with Pages when you perform a copy/paste. For instance, Pages has no clue about Word Bibliography, Citations, or References. I think that is what those parentheses are in your enclosed content.
You may try a couple of approaches:
- Open that Word document in another Pages document and then copy/paste that selection between Pages documents.
- Select that text in Word and then click, hold, and then drag that text from Word to the Pages document as in the following animation… (Refresh your browser ⌘R to replay the animation as I have limited it: