My AV software - Trend Micro - identified EXPL_PDF4155.A as a threat and deleted the 1.7.7 installer at the last scan. I had already used the installer and installed xAMPP, so no problem to delete the files but is the installer really infected or is it just a false positive.
If you do a checksum comparison of the download, and the result is true - you may safely assume TrendMicro has made a false positive. (that's why checksums are provided)