I'm afraid your problem is the ever present 'China factor' (note HK and Taiwan are exempt) in regards to excel being used for spec'ing projects. You have possibly come across one of the following situations:
A: The pirate copy of word/adobe acrobat has failed and they are too lazy and or incompetent to get a working copy installed.
B: Too lazy and incompetent to work with anything they don't know already, (took me an age to wean my graphics slapper off Coral Draw and join us in the year 2000+ which uses illustrator). Thus you have sent a file they don't like the look of and are unwilling to use it as it would divert time from shopping on taobao or playing happy farmer. This may save them 5 minutes and cost you an hour but better your time than theirs.
Now you could go about having them actually installed a copy of adobe reader, point out it's freely available. But as ho jie town is probably in the middle of nowhere of a middle of no where province, so common sense is probably in short supply. The only true way to get them to change is to be personally on hand to deliver the universally understood sign of dissatisfaction, this being a slap to the back of head, which is hardly worth the plane flight.
However being a supportive type you could always use the following freeware for spec'ing projects:
Which is at least as good as MS project, yet 100% free as I have been informed by my French friend, he also recommended the use of pictures as these are normally more easily understood and digested by the 中国人。
Hope it helps.
3.5 years in and counting the days to release.