# How to add a 3rd party library in sharepoint 2010 event receiver

I am writing a SharePoint item event receiver to OCR documents that are uploaded/added to a library to generate searchable PDF for that document. I'm using a third party library (dll) "tesseract.net.sdk" to convert the input pdf to searchable pdf.

I am using visual studio 2015 for sandbox solution deployment to a SharePoint 2010 farm. I have added the external library (dll) using the package external assemblies option but when I try to deploy the project it gives following error:

Could not load file or assembly C:\Users\test.user\AppData\Local\Temp\solution-3a181ba8-d203-45c8-8567-c3b0b459ef32\cab\tesseract.dll or one of its dependencies. The module was expected to contain an assembly manifest."

The exact Windows dll is having a problem with is the tesseract.dll.

Please let me know how can I add this dll to my package (wsp) and correct the error I'm encountering.