Around signature and on the top of each page of a pdf, there is "bolosign" marking. After discussing with the team : "it's for security reason" and "We cannot help you in this case unfortunately as all eSignature platforms have this." My legal team says they cannot use a contract on which there is extra marking.

Also, this isn't true, all platforms don't make this marking mandatory. For example bunnydoc has a simple option in the settings to remove all markings... https://appsumo.com/products/bunnydoc/#overview