Pitstop server 4 pdf dimension bigger than Pitstop server 2

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Hi everyone,
I have tried to process a lot of pdf with Pitstop Server 2 and Pitstop Server 4 with exactly the same Action List and Pdf Profile, but pdf processed by version 4 are 30-50% bigger than version 2. After a lot of tests no solution about this problem..
What can I do? Maybe ps4 put inside pdf more info than 2 that cannot be modified with works on Action and Profiles and should I keep these size?
Thanks