iOS Safari opens PDFs directly. It's a file format with native support. I don't know why the OP had to do those steps, as that never happened to me... maybe the

iOS Safari opens PDFs directly. It's a file format with native support. I don't know why the OP had to do those steps, as that never happened to me... maybe the site hosting the PDF informed the wrong MIME Content type, so the file was downloaded as a generic "binary" file.