[Editing PDF's]

Hi there, 

I'm strongly considering buying Affinity Publisher to edit my self published books. I have a specific question about it's ability to edit PDF's, which is this: 

I format my novels using Vellum and export the print copy as a PDF. I'd like to embellish each first page of my chapters with my own headings (see attached image). Vellum doesn't allow me to have headings that span the entire width of the page. When I edit the PDF in Adobe Photoshop, it stops the text being a vector, which means that the finished, printed result leaves the text looking rough and pixelated. So, would I be able to use Affinity Publisher to add these headings to my finished PDF manuscript and still keep the text as a vector, remaining sharp and crisp? Is the software able to do this? 

I hope that makes sense! Thanks for any help that I may receive. 

Terry Kitto