The technical term for the line on the left (or right) is a "rule."
You do not want to use the pipe character but rather a line in the header.

Numbers were originally done in the headers (Word 95 - Word 97). Most people do them now using the line numbering option. That, however, is not uniform, giving numbers for actual lines of text, rather than uniformly spacing down the page. To do this in Word 97 you would use a borderless frame or textbox in the header in a Word template and then use that template as base for new documents.

• Templates in Microsoft Word
• Recap of Header-Footer Settings
• Frames and Textboxes in Microsoft Word

I am an attorney in a jurisdiction that does not require such for pleadings. Such numbers still are used here in transcripts. I am a throwback who does use rules in his pleadings. I will, if you want, produce such a template for you with 26 numbers in the Courier New font on the left side of the page.

If you are not an attorney, I am amazed that a court is requiring to follow formal rules. If you are, you really need to upgrade your software because Office 97 is not secure.