Hello,
I just tried limesurvey and It seems that the PDF export from statistics doesn't print group infos, as the group name, but it just print question after question. I search in parameters but didn't find anything to modify this. Is that possible to add this information? 
Thanks

Bug report ?
community.limesurvey.org/bug-tracker/

Hi,
in my opinion this is not really surprising.

In "statistics" you only expect the results of questions, not more (pure numbers, counts, means, averages,...)
The same you see (only questions) displaying as HTML
And you do not see any groups when you export the data.

Statistics are not affected by any logical grouping in LimeSurvey.
Groups are mainly used for logical reasons (randomization, javascript, conditions) but not for semantic reasons (introduction, main part, demography, or whatever)
So why display them in statistics?

Statistic is not a report.
If you would like to have a well designed report, export your data and use your analysis tool

Joffm