Ruby on Rails

Problem: I have use the net/http code for uploading the '.doc', '.docx', '.pdf' and images files on dropbox. But I getting the issues like:

1.invalid byte sequence in UTF 8
2. Now while the file is uploading but it not uploading the content and even it uploading as a corrupt file.

Below I writing my code to upload the file on dropbox. Please help me.

Code:

uri = URI.parse("https://content.dropboxapi.com/2/files/upload")
          request = Net::HTTP::Post.new(uri)
          request.content_type = "application/octet-stream"
          request["Authorization"] = "Bearer #{$acess_token}"
          request["Dropbox-Api-Arg"] = "{\"path\":\"/Sass-for-Web-Designers.pdf\"}"
          request.body = ""
          request.body << File.open("app/assets/images/categoryImages/Sass-for-Web-Designers.pdf").read
            #request.body << file.content
            #file.close