Can I post multiple files at the same time?

Yes!!
However, it only seems to work if you post these multiple files into a folder on Moodle. (If you try to post several files to a single link on a Web page, only the first file seems to appear when the user clicks on the link.)

You can go to the folder, click on edit, and then click on "Add" and select as these files from the "Recent Files" area and be sure and click "Save and return to course" when you are finished. If you want to upload multiple files without selecting them one at a time from your computer, yo can zip them into a zipped file and upload the zipped file into the folder. Then if you click on the little box to the right of the zipped file, you will have the option to unzip the zipped file. This will crate the individual files and also leave the zipped file in the folder.

Warning: be sure the size of the zipped file doesn't exceed the maximum size of files that you can post. Currently the maximum size is 8M.