Attachment File Break To Several Pages

So i just sent Sales Invoice to client through ERP, the preview of the SI is 1 page, everything looks normal… But after the email sent, i check the sent email and found out that the attached Sales Invoice file (PDF format) break to 3 pages… i am confused as the preview was good, fit in 1 page but after sent it through email, the file format just not good anymore…

anyone experienced this ?