We want to mix an eps file with a ghostscript file. The eps file is our formular style and the ghostscript is for the texts. After this we create a pdf with the new file.
Whenever we do this, we get 2 letters, one with the text and one with the formular.
There is no such thing as a 'ghostscript' file, possibly you mean a PostScript file ?
You can supply two PostScript programs to Ghostscript, and in general provided the first does not execute a showpage, the second will be printed 'over the top'. Valid EPS files do not contain a showpage.
You can also redefine showpage as a no-op, run the first program, then run the second program then run the original showpage.