MSIEXEC.EXE may not know how to expand the __download folder.
TRANSFORMS="__Download\AcroRead.mst"
suggest:
wait {pathname of system folder}\MSIEXEC.exe /i "{pathname of file "__download\acroread.msi"}" PATCH="{pathname of file "__ Download\AcroRdrDCUpd1502320070.msp"}" TRANSFORMS="{pathname of file "__Download\AcroRead.mst"}" /qn