ITextSharp and embedded fonts

I have an existing PDF (original PDF) with some text using the ARIAL font. I need to convert my original PDF to PDF / A-1b. To do this, I simply create a new PDF / a-1b, set the required xmp and copy page from the standard PDF (using getImportedPage

in a loop). But I don't know how to "force" the font to stick on the existing text that came with my original PDF.

Is it possible to link a font (and embed it in PDF) for existing text?