DXF files are large and show no picture until a CAD program or viewer opens them. PNG keeps every pixel exactly and supports transparent backgrounds. DXF is at home in passing a drawing between different CAD programs, or to a laser cutter or CNC machine; PNG is the usual choice for screenshots, logos, graphics with text or transparency. The result is a picture of each page, so its text can no longer be selected or searched.
The defaults suit most files. Under Options you can resize the result.
The drawing is shown as its model space, fitted to the extents of what is in it. If model space is empty, the first layout that has objects is drawn instead. Objects on layers that are switched off or frozen are not drawn. The PNG is 2400 pixels on its longer side unless a size is chosen under Options, on a white background unless another colour is chosen; AutoCAD's colour 7 is drawn black on a light background and white on a dark one. The browser has none of the fonts a drawing names, so text is drawn in a built-in font with Latin, Greek and basic Cyrillic letters and the usual symbols (m², Ø, ±, °). Chinese, Japanese and Korean text appears as empty boxes.