How do I add text to PDF in bitmap format?

Q: I’m using PDFNet(.NET 4.0 version), I am wondering whether I
can create a PDF document by inserting bitmaps which is based on the
pure strings. For example, I want to insert a bitmap whose content is
a hieroglyphic-like image and this string is based on the specific
text string during the running of my program.

A: It is not clear whether you want to insert a bitmap (from a memory
buffer) or a piece of text in a specific font?

You could technically use GDI+ to render a piece of text to
System.Drawing.Bitmap, then insert that bitmap to PDF using
pdftron.PDF.Image.Create() as shown in AddImage sample project:

You can also do without GDI+. For example, simply draw text to a temp
PDF page (using ElementBuilder/ElementWriter), rasterize the page (or
a page subset) using PDFDraw.GetBitmap(), then place the raster image
on the final PDF page.