I tried to convert a PDF file to an image. But there is a error with the character width computation. As you can see inside the blue box, there are gaps after every umlaut mark (ä ,ö ,ü). Some characters in the font doesn't contain any width information. The distance between the character is handled by position adjustment. For example:
[1., -278, ), -844, H, -722, ä, -556, u, -611, sliche P, -667, f, -333, lege] TJ
I guess there is an error in the font.getWidth() implementation. If I call font.getWidth("ä") it returns 556. (Instead of 0, what would fit)
I attached the PDF and the converted image.