General printing to an image file isn't something you want to do if you can avoid it. If the content is primarily text, the image file would usually be much, much larger than the text equivalent, would require special software to display it, wouldn't support page breaks, and so forth.
When you do a "print to file" operation in Linux/Unix, the normal operation is that the printing code or application produces a PostScript (.ps) file. PostScript can contain images, but also provides a more efficient means of containing WYSIWYG text. In fact, PDF files are specialized extensions of PostScript. Typically if you have a bitmap image in a PDF, it will encode that image in TIFF form.
Although you can buy printers that print PostScript directly (one of the most famous of them was the Apple LaserWriter), Linux has the ability to convert from PostScript to any other Page Description Language, such as HP's PCL. There is an app for that. It's called GhostScript.