I have a dashboard with 5 panels (All showing statistics). We I use the schedule PDF delivery option under export menu, Data in few columns in the panels are missing (data is appearing blank). To confirm on it, I have manually exported the dashboard into PDF, still the columns are missing.
Does your dashboard use custom visualisations? These wont work with the built-in scheduled PDF delivery. If you want to have a complex dashboard emailed, you can use this app: https://splunkbase.splunk.com/app/4030/
It's quite a nice app but might have some requirements that mean it isn't suitable for your environment.