When you paste into GN4 a text from a PDF, if you didn't use Paste text as one paragraph, the text flow broke and every line becomes a single paragraph.
This is not avoidable and is not GN4 related - the same problem happens when pasting from PDF in Microsoft Office and other editors.
Moreover, even if the text was correctly indented in PDF, the indents (as possible markers to help to restore original paragraphs) all disappear after paste.
The only remedy is to convert all paragraph signs (EOPs or ¶) in spaces, making the entire text one paragraph, and then to restore manually the original paragraphs, by looking in the original text and pressing return where needed.
Find the GN4 tool that convert all paragraph breaks to spaces in Edit menu (Edit > Find > Replace ¶ with Spaces in Highlighted Text).
To get rid of extra paragraphs
1.Highlight the block of text where you want to perform the replacement, and then on the Edit menu point to Find, and then click Replace ¶ with Spaces in Highlighted Text (in older version of configuration: Replace EOPs with spaces).
To restore the original flow
Look at the GN4 text side-by-side with PDF text, and then in the GN4 text press the 8 key where in the original text starts a new paragraph.
See also