I just uploaded a PDF (download the file here: https://www.dropbox.com/s/ysjy28e0a914rpf/5466493ef2148.pdf?dl=0 ) and opened using the Cloud Viewer from my account.
It takes more than 40 seconds just for start showing the content, and if I try to do annotations I have to wait the same time. The file is just 1.4Mb.
While viewing the document it shows a message saying “Loading content” of each page I try to load and have to wait less than a second.
I’m trying your product but with this poor performance will be impossible to use.