As you re-assemble 'dis-assembled' documents, the formatting of the new (or augmented) document may not appear the way you wish. This is invariably a function of the styles and formatting of the base documents. See Styles discussion for the benefits and the frustrations of this crucial aspect of Word.
Therefore, before you assemble your first document from your new collection of dis-assembled text, take a peek at each document. Look especially at the formatting, indenting, etc. associated with the last paragraph marker. (If you don't 'see' it, click the 'Show All' button (the pilcrow character (¶)) on the Home tab. It is that last paragraph marker that affect the appearance of not just the last paragraph, but the next paragraph you type or call in. If the 'Enter' on the last line of the document suggests a number, bullet, tab, indent or otherwise a modification from 'Normal,' you need to consider if this is what you want.
If you want the next paragraph that you type or insert (or that will be called from document assembly selections) to be independent of the previous text, make sure that you add a new 'blank and normal'. Be sure to 'un'- number, 'un'-bullet, 'un'-indent, 'un'-tab or otherwise undo the formatting so that the next block of text comes in 'clean.'
If after all that undoing, you still have something you don't like, use the 'Format Painter' to normalize things. Click 'Format Painter' in a 'normal' section of text to capture that 'good' formatting. The 'Format Painter' button will be toggled 'depressed' (i.e., 'on'). Move your mouse to over the last line of the document and left-click the mouse. That should apply the proper formatting.