Are you using Acrobat ?
Do you want to perform this with Acrobat ?
If this is a PDF,you could convert this to an excel file and easily add what you require.
"I would like to add my own row..."
Not possible. Follow sukritd's suggestion of exporting the PDF content (select "Spreadsheet").
You would use Adobe Acrobat Pro or a subscription to Adobe's Acrobat Document Cloud PDF Services Export PDF service.
Good to know is that most times programmatically created PDF from database queries results in "bare bones" PDF under the hood.
Typically these PDFs offer little support to the export of content.
The bright note is that when a well-formed tagged PDF is provided export is optimized.
"Tagged" PDF is designed to support export and accessible PDF.
A PDF that complies with ISO 14289, PDF/UA (ANSI/AIIM/ISO 14289-1, $15 from AIIM) would be the "well-formed" PDF.