Ai PDF quality loss in CorelDRAW

[saraht18892164]

I have a logo design, created in Illustrator CC, saved as pdf (Illustrator default/editing capabilities preserved/no downsampling) and sent to a friend in China, who is trying to get it printed as a large-sized sign at a print shop there.  The print shop apparently uses CorelDraw, and when they tried to scale the image up to the large size, lost significant quality.  I have no direct contact with the printers (and language barrier would probably prevent any communication, even if I did).  Any ideas what could cause the quality loss, or if there is a better file format I should send them to make it most likely to work well?  Thanks for any ideas!

[Monika Gause]

Which features did you use to create the logo?

[saraht18892164]

Just text (for which I created outlines) and a basic vector illustration - no special effects or anything.

[Monika Gause]

Then please show before and after.

[Stephen_A_Marsh]

They may find that EPS works better and you may also consider saving as an earlier version of Illustrator like v3.0 format to potentially make the file more compatible with other programs (which may make it more complex by expanding effects etc). Open the EPS file back into Illustrator to ensure that it looks as intended (this is not a guarantee that Corel Draw will have the same results).