COREL DRAW

If you are working in Corel it is not necessary to save the document in some other format, but send it in original CDR format. It is very important that all textual parts in which some of the fonts have been used are changed into curves (arrange/convert to curves)

 
ADOBE ILLUSTRATOR

If you work in Illustrator it is necessary to send the document in EPS format and not the original AI extension. In Illustrator it is necessary to change all fonts into curves (type/create outlines)

 
PDF

PDF is format good for printing especially for making of catalogues, brochures, books...

 
FONTS

For textual parts one should not use system fonts which contain Cyrillic characters.