Edit2: I just figure out how to make the percentages work, in limesurvey\application\helpers\admin\statistics_helper.php where the 3D pie chart is created the "setFontProprieties" was poiting to '$rootdir."/fonts/".$chartfontfile', but the fonts are in '$rootdir."/assets/fonts/".$chartfontfile'. Now I just need to change te text.

Update to the latest version, see if the problem persists. If it persists: make a bug report. Your changes might be overwritten by any future update you might make, so I think it is best that it is fixed in the core, rather than you hacking the code. Might be a temporary solution, but is not future proof.

So a year later I still have the same issue! Thankfully, I found the problem, and set up a workaround.

ISSUE: PDF legends on pie graphs and other graphs have no text. I found the problem by setting debug to "2" in the config.php file. This showed a number of PHP warnings linked to pChart.class.php and specifically a link to a missing file found along the path /HOMEDIR/fonts/DejaVuSans.ttf. It turns out that there is no fonts folder in this location, but there is one along the path /HOMEDIR/assets/fonts/DejaVuSans.ttf. I'm guessing this is because I have upgraded (properly) a number of times, and somehow the MySQL database still has a reference to the old path.

WORK AROUND: For now, I just created a symbolic link so that /fonts points to /assets/fonts. At some later date, perhaps I'll track down the error in the database.

NOTE: This seems somehow related to this bug report: bugs.limesurvey.org/view.php?id=13338

My current LimeSurvey version 3.16.1+