We classify whether an uploaded file is a presentation or a document on the following basis:

• If the uploaded file is a ppt, pptx, keynote or odp, it is a presentation
• If the uploaded file is a doc, docx, IWork pages or odt, it is a document
• If the uploaded file is a PDF, we look at the aspect ratio (height v/s width) of the file

1. When uploaded as a PDF, if the file has a higher width than height (like the 4:3 aspect ratio of a presentation slide), it is a presentation
2. If the file has a higher height than width (like a standard A4 document), it is a document

Sometimes, a ppt or pptx file can also end up in a document format. For instance, you want to generate a PDF with a ppt. While doing this, you printed it as a PDF in the "Notes pages" mode. Now, this PDF will have the shape/size of a document. If you upload this to SlideShare, our convertor will recognize this as a document. If you do not want this, just generate the PDF in standard mode and upload again. This will show up as a presentation.

 For better understanding of this, view this example.