How to get OCR API working with signed s3 urls

We are using pro version of your software and have a question regarding OCR. In our app, user upload files and we store them in s3 with restricted public access. We are generating signed url with S3 to get OCR details which gives temporary access to file. But we are getting the following error message

{ "OCRExitCode":3, "IsErroredOnProcessing":true, "ErrorMessage":["File failed validation. The image URL is invalid or the access is restricted. Please check if the image URL is correct and is accessible."], "ErrorDetails":"","ProcessingTimeInMilliseconds":"632" }

S3 signed urls looks like this (AccessKeyId removed :wink: ) :
https://testbucket.s3.ap-southeast-2.amazonaws.com/bills/bill1.pdf?AWSAccessKeyId=AWSKEY&Expires=1541324491&Signature=f897zWOyxfgAhfb9ANdsLwauqUfE%3D

Can you let us know how to get OCR working with signed s3 urls?

Does it work if you set filetype=PDF?

See Free OCR API

Yes, setting filetype worked.

Thanks for the prompt response.