You can convert one or more selected images into a multipage TIFF file within
ACDSee.

To create a multi-page TIFF file:
  1. Select the image(s) you want to include.
  2. Click Tools | Convert File Format.
  3. Select Tiff.
  4. Click Next.
  5. Click Next.
  6. In the Output area, select Merged.
  7. Click Start Convert.
  8. Click Finish.