It is what is is. One works and builds upon what there is,reality. As it is,
And if you want…there is a Vatican web page with all his speeches and there are his daily homilies, twits , and so on.
As from the other Popes.
And also, normally , at this level of conversation , when they are writing together a document like this, it is because they know about each other and what they represent and believe in.
It is an ongoing dialogue also as a whole that started long ago.
There are letters from different Popes to different brothers and sisters of different faiths.
Most you will find either in Vatican site or Vatican news or probably searching into your USSCB web page,
There is a whole lot to read, probably more than one has time to.
You will probably understand a bit more after doing a bit of that reading.