是特指吗？

file是"文件夹",paper file是用paper来给file作定语了.

应该是"装纸的文件夹".
如果是电子的,电脑上的,就不是paper file了,而是只用一个词file.

例:

1. At present, compared with paper file, electronic file is a more careful and difficult work.
摘要电子文件与纸质文件相比，这是一项更为细致且难度较大的工作。

2. Just as you keep copies of all letters in a paper file folder, you should keep copies of all letters on your computer in the directory for that client.
就像把信函的副本保存在一个纸文件夹中一样，您可以将信函的电子副本保存在电脑中专门为该客户建立的文件夹中。