LaTeX porting *.eps images with eps2pdf and german umlauts (mutated vowel)

I draw a use case diagram with MagicDraw and save it as EPS file. Now I want to integrated it into my TeX file by using eps2pdf. It works so far, but the picture includes german umlauts like ä,ö or ü and they will be shown as "?" (question marks).

What could I do to solve this problem?

Greetings, Lony

Important packages:

\usepackage[ngerman]{babel}
\usepackage[T1]{fontenc}
\usepackage[latin9开发者_如何学运维]{inputenc}
\usepackage{lmodern}
\usepackage{epstopdf}
\usepackage[pdftex]{graphicx}

Maybe try to embed all fonts in the PDF file?

As far as I remember, this code should do it:

ps2pdf14 your_image.eps

And BTW, you can check if your pdf embeds all fonts using pdffonts