When my app runs (or when I run from commandline) the wkhtmltopdf command I get the following error: (showing it from command line)
#> wkhtmltopdf
wkhtmltopd
Note that there is an executable version of wkhtmltopdf distributed in a UPX compressed format, ldd and file will both report that this file is statically linked even though the payload requires shared libraries.
To check try
strings | fgrep UPX
If you see any "UPX" id strings then install upx and use "upx -d" on a copy of the file (as upx works in place) and then run ldd on the uncompressed file.