PDF size output difference BOXI3 vs BI4

In SBOP EDGE BO XI 3.1 SP5 WebIntelligence Reports are exported as PDF and send to recipients by mail.

After upgrade to version SBOP EDGE BI 4.1 SP5 on new hardware the same documents are exported as PDF and send to the same recipients by mail.

Comparing the PDF size gives a significantly larger size for PDF documents exported with BI 4.1SP5

One specific document has even a doubled size in BI4.1SP5 (30MB instead of 15MB in BOXI3) and is now not able to be send out by mail. Our exchange servers will not allow this.

This specific document has 1000 pages with 3 or more graphs/charts on every page.

We suspect it has to do with the charts converted to JPG images in the PDF. "output.dpi" setting in caching_media_profiles.xml in both win32_x86 and win64_x64 folders are set to 96 as is in the BOXI3 environment.

Please advice how to decrease PDF size in BI4.1 to the same size as in SBOP EDGE BO XI 3.1