When you paste into GN4 a text from a PDF, the text flow broke and every line becomes a single paragraph.
This 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 remedy is to paste all text as one paragrah, and then to restore manually the original paragraphs, by looking in the original text and pressing return where needed.
To paste text as one paragraph
On the Edit menu point to Paste, and then click Paste as one paragraph.
To restore the original flow of paragraphs
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