I think all documents coming from a Mac PC can suit an iPad. Is that true?
Well, in general the answer is yes. But it's a bit more complicated than that. It depends upon the program that created the spreadsheet, not the hardware that was used. If you are using Microsoft Excel (on a Windows PC or a Mac) you can import the file to your iPad as discussed above and then use a program like "Numbers" on the iPad to edit the spreadsheet. You can also use iPad apps like Documents to Go, QuickOffice, or Office HD to edit the spreadsheet. Likewise, if the Mac used Numbers to create the spreadsheet, Numbers on the iPad can read the spreadsheet. (I don't believe that the other apps can do so but I may be wrong.)
However, none of these solutions can be guaranteed to preserve the original spreadsheet precisely. That's even true of Mac Numbers -> iPad Numbers. (The latter version of Numbers, though they're both Apple products with the same name, does not have all the functionality of Mac version.) And it's absolutely true when trying to translate a Microsoft Excel spreadsheet into a format that an app on the iPad can read. The problems usually occur only with complex spreadsheets with formulas or complex formatting but they do exist. The reviews Tim cited above can provide some specific details but about the only way to be sure a particular solution works for you is to give it a try with the spreadsheet you're trying to edit.
The good news is that if you purchase one of the iPad apps (e.g. Documents to Go, Numbers, etc.) and find that it doesn't work for you, you can certainly get a refund by contacting Apple customer support as described in iTunes.