应该是let.
please let the letter of credit to read "allowing transshipment"
意思应该是：让信用证上显示”允许转运“的条款
read 在这个地方应该是有显示的意思,字面看就是在信用证上能被读出来,正如,文档中,"the letter says..." ,文档上的东西被显示不一定就用"wrote down""added"之类的.