As well as exporting, Sketch can also import various file formats as well. You can simply drag-and-drop files onto the Sketch icon in the dock, or directly into an open document.
PNG, JPG, TIFF, and WebP bitmap image files are supported for import, whilst Sketch can also open the vector formats SVG, PDF, and EPS.
If you’re importing a PDF document with multiple pages, each page will be imported separately and given its own Artboard.
AI and PSD files have limited support, and can only be opened as a single flattened layer.