- Normally the best way to create an add is to to do it and to export it as PDF/X-4.
- From Photoshop you can save as PDF, choose either the standard as the printer asks for or save as PDF/X-4.
- Never use in any case EPS.
- If the add contains vectors and/or fonts PDF is the best file type.
- If no text or vectors are used you could use JPG with high compression quality, tiff or (not in your case) psd.
Take care that
- Your file is not flattened to background, so all layers are alive, otherwise fonts will be rasterized.
- You file should have a resolution in minimum between 240 and 300 ppi (not dpi)
- With the text: is it pure black or is it 4c-black? K-Black is easier to accomplish in InDesign.
- Don't make small elements in 4c.