Question

And this is turn means copying the original as closely as po

Answer 1

由于看不到整个语境,只能怀疑 is turn 应该是 in turn 之误.

从语法角度而言句子不存在 this is turn means 这样的句型.

in turn 是俚语用法,转折语气,表达和前文做出的对照.

其他部分你理解的没错,去掉 is turn (in turn) 的话就是

“这意味着要尽量复制得和原件（原稿、原版）一样”

如此参照着前文看,你应该能够解读出整段话的意思了.

如果还需要解释,欢迎补充后追问...