Use your Kotak customer ID or registered mobile number as the password if that is the format used in your statement
Try your date of birth in DDMMYYYY format if the PDF asks for a DOB-based password
Try your PAN number in uppercase if the statement uses PAN as the password
Check the email or SMS from Kotak for the exact password format mentioned
Open the PDF in a PDF reader and enter the correct password when prompted
If you do not know the password format, log in to Kotak Net Banking or the Kotak Mobile Banking app and download the statement again
Contact Kotak Bank customer care or visit a branch if the password still does not work