Yes. Sort of.
Ink is what Adobe calls there pen.
So from what I am reading here is that what you are asking is can I edit a PDF file with a stylus on an iPad.
The answer to that is yes, there are apps for the iPad that work with a stylus that allow editing of PDFs.
Apps like PDF Expert 5 allow for this.
You do need to buy the app though. Adobe's free Line and Sketch apps that are designed specifically for Ink and Slide don't open PDF files natively. You'd need to convert the PDF file to an image which I would guess is not really what you are after.