To search multiple historical newspapers at the same time, click on the "select multiple databases" link on the ProQuest search screen. When the next screen displays, scroll down to the historical newspapers section and choose the titles you would like to search, hit CONTINUE and proceed with your search.
In order to search for newspaper content of a particular type (e.g. editorials or ads), click on the ADVANCED SEARCH tab. Choose DOCUMENT TYPE from one of the drop down boxes, and click on the "Look up document types" link that pops up, and click on the ADD to SEARCH box next to the document type you want to find. Then enter your search terms in the other available search boxes.
The search within the PDF text option, which should allow you to find your search terms within the article, DOES NOT WORK MOST OF THE TIME!