The affairs of foreign trade are numerous and cumbersome, so many small details will be ignored by us. For example, many people tend to ignore such a detail: is the format of the document file that you send to your customers! Are you used to attaching a quotation for Excel or Word documents to your e-mail? What about the echo? In fact, there are reasons. Considering that many viruses are disguised as Excel and Word documents appear in the mail, most companies in Europe and the United States have adopted spam filtering in their mail systems. As long as the documents are attached to Excel and Word documents, Delete all. Therefore, it is impossible to estimate the losses that may be caused by delays in quoting and communicating with customers. The best way to solve this problem is to make the document into a PDF document. PDF documents are one of the most popular documents in the world. At present, no virus can disguise itself as a PDF file or parasite in a PDF file. PDF documents can be compatible with any system, such as Window, Linux, Unix, Mac, etc. We send the quotations and technical documents into PDF documents and send them in the mail. The customer's mail system will not mistake the mail for spam or virus mail. E-mail can successfully enter the customer's mailbox and open the door to trade. To change a small detail, why not give yourself a little more chance of success?