Extract Lidar raster in format compatible with online print shop

[Bud]

ArcGIS Pro 3.4.2

Background:

The Ontario government has lidar raster data available as an image service layer: 
https://ws.geoservices.lrc.gov.on.ca/arcgis5/rest/services/Elevation/Ontario_DTM_LidarDerived/ImageS...
I've clicked the ArcMap link to download a layer file: Elevation_Ontario_DTM_LidarDerived.lyr. 

I can open the .LYR file in ArcGIS Pro. The default symbology is "Stretch".

Question:

I want to export the subject area and print it at a large format print shop such as Walmart Photo Centre (Canada). The file requirements are: "...Images in .jpg, .JPG .jpeg, .JPEG, format. Maximum image width is 8000px, maximum image height is 8000px, maximum file size is 16mb."

How can I export the lidar raster image service as a JPG that is a 2:3 aspect ratio, max 8000x8000 pixels, and less than 16mb, while getting as close as possible to those limits to maximize photo quality?

[Bud · Accepted solution]

1. Right-click the layer in the Contents pane > Data > Export raster. Export as a TIFF.
   
2. Using the resulting file:
   Now that we're dealing with a smaller subject area, change the symbology to Shaded Relief. The raster symbology shows up better with a smaller subject area because the gradient has a smaller range of pixels, so there's more contrast.
   
3. Export the raster to a TIFF again, but this time enable "Use Renderer" and "Force RGB". (We can't export as a JPEG because we'll get an error.)
   
4. Open the new TIFF using GIMP image editor: https://www.gimp.org/.
   Hint: If you don't have Windows admin rights on your computer, choose to install "Only on my computer".
5. In GIMP, crop the image to a fixed aspect ratio: 2:3 (landscape). Hit Enter to commit.
6. Image > Flatten Image.
7. Image > Scale Image. Scale it to less than 8000 pixels x 8000 pixels.
8. File > Export As. Change "Select File Type (By Extension)" to "JPEG image". Export.
9. In the Export Image as JPEG window, we have the option to change the quality. Play around with different quality settings until the output file is less than 16mb.
   There isn't a way to preview the output size, so we have to do it the hard way: export at a given percentage, check the file size, if it's more than 16mb, then try a lower quality setting. Repeat.

Now, upload the image (less than 8000px x 8000px; <16mb; 2:3 ratio) to the online printing service.

Note: The GIMP workflow works for Archives of Ontario historic black & white photos, too:   https://www.archives.gov.on.ca/en/aerialphotos/index.aspx. 
As well as for infrared and ortho imagery ordered from the Ministry of Natural Resources.

An alternative print service is PosterJack.