What version of LimeSurvey is used?
I'm not aware of a setting via GUI in LS 3. Perhaps there is a config-setting to change such a format.
The pdf library default settings are in the file.
github.com/LimeSurvey/LimeSurvey/blob/ma...ion/config/tcpdf.php
Some settings are exposed to the config files, but the pdf pageformat seems not to be exposed there.
github.com/LimeSurvey/LimeSurvey/blob/ma.../config-defaults.php
But would be a good feature request via GUI (in case someone is not Admin and can change phpfiles): Statistics Export Settings:
Setting Page orientation (Portrait or landscape orientation)
Page format (A4, US Letter)
You can open a feature request.