How can I translate "To all to whom these presents shall come, Greeting"?
This sentence construction has roots in Common Law, and indeed some care should be taken when translating it in full. For example, one of the answers in the ELU link notes that these presents is a legal term for "this document".

As for the phrase itself, Chinese Wikipedia has a handy footnote about the phrase:


  这两句都有两个to而且合乎文法，关系代名词whom前面写to是老式文法，现代英文关系代名词一般直接接在all后面，to移至动词come后方，“To all to whom these presents shall come, Greeting”即“To all whom these presents shall come to, Greeting”，come to意为‘涉及’，presents意为‘文件’，“To all whom these presents shall come to, Greeting”意为‘致本文件所涉及之诸位，各位好：’；‘致本文件相关各方，大家好：’


So you can translate using:


致本文件所涉及之诸位，各位好
or
致本文件相关各方，大家好