添付ファイル参照下さい。って英語でなんて言うの？

1. When referring to something you have sent with your email, you may say - 'please see the attached file' and this will refer the receiver to that attachment.
   "I sent you a load of photos from the holiday. Please see the attached file."
2. An alternative is 'Please see attachment.' It means exactly the same thing, but the message is in note form. When writing in note form because you want to send the message quickly, you may omit the articles 'a' or 'the - and even the personal pronouns I, You, We etc.'
   "See you Monday on boat, bring beer!"

Depending on what the message is about you can use any of the sentences above.
For example:

Dear Sir/Madam,

In reference to our discussion in the meeting today, I have attached the form.......

OR
Dear Sir/Madam,

Thank for the meeting today. It was very fruitful and I hope we do business together. I have compiled all the information you need.

Please find attached.

Regards,

Yuan

If you have written some details and would like them to refer to a specific file or page, you could say "for further details on (this subject) please refer to (page no. __ in) the attachment '(file name)'.

I have attached a file for your convenience.' - This is used if you are giving someone some extra information that might be useful to them.

All of these are ways you can tell someone to refer to the attachment.
They can all be used in a formal business email.

1. Please refer to the attached file.
   This statement is asking the reader to access and take note of the attached file.

2. I have attached a file for your perusal.
   Perusal means the action of reading or examining something.

Please refer to the attached file
Please refer to the attachment
If you would kindly refer to the attached file

Are all examples of phrasing which is suitable for inclusion in a business e-mail.

"Snail mail" is rarely used in today's fast paced business environment...We now regularly send documents as attachments to our emails ( literally;-)
"Remember I have sent those documents by email. So please see the attachment"

"Please see the attachment below." This asks them to look at the file you have attached to the email.

"Please take a look at the document attached." This is another way of asking them to look at the document that you attached to the email.