I downloaded the PPD file from the URL you provided and I also downloaded an archive the PPD was looking for (the Strawberry Perl PPM doesn't seem to like using repos), and I got it installed.

However I still got the same message saying the Net-SNMP library can't be found.

FYI the results of the install are as follows:

G:\perl>ppm install G:\downloads\Net-SNMP.ppd
Installing package 'G:\downloads\Net-SNMP.ppd'...
Use of chdir('') or chdir(undef) as chdir() is deprecated at G:/perl/perl/vendor/lib/PPM.pm line 393.
Installing G:\perl\perl\site\lib\Net\SNMP.pm
Installing G:\perl\perl\site\lib\Net\SNMP\Dispatcher.pm
Installing G:\perl\perl\site\lib\Net\SNMP\Message.pm
Installing G:\perl\perl\site\lib\Net\SNMP\MessageProcessing.pm
Installing G:\perl\perl\site\lib\Net\SNMP\PDU.pm
Installing G:\perl\perl\site\lib\Net\SNMP\Security.pm
Installing G:\perl\perl\site\lib\Net\SNMP\Transport.pm
Installing G:\perl\perl\site\lib\Net\SNMP\Security\Community.pm
Installing G:\perl\perl\site\lib\Net\SNMP\Security\USM.pm
Installing G:\perl\perl\site\lib\Net\SNMP\Transport\IPv4.pm
Installing G:\perl\perl\site\lib\Net\SNMP\Transport\IPv6.pm
Installing G:\perl\perl\site\lib\Net\SNMP\Transport\IPv4\TCP.pm
Installing G:\perl\perl\site\lib\Net\SNMP\Transport\IPv4\UDP.pm
Installing G:\perl\perl\site\lib\Net\SNMP\Transport\IPv6\TCP.pm
Installing G:\perl\perl\site\lib\Net\SNMP\Transport\IPv6\UDP.pm
Installing G:\perl\perl\bin\snmpkey
Installing G:\perl\perl\bin\snmpkey.bat

PS - I also had to download Net-SNMP-v6.0.1-PPM516.tar.gz