I am attempting to make a change to a flyer which was created in Adobe, and have been unsuccessful thus far. Can one please advise how I can make changes to an existing Abobe file (which I did not initially create)?
Asuming you are talking about a file in PDF format, it can't be edited with the free Reader. Acrobat can do it to some extent. Major editing is best done in the original file from which the PDF was made.
Bear in mind that there is no product called just 'Adobe'. Maybe someone said that and you assumed Adobe Reader, but perhaps it was Adobe Illustrator or Adobe Photoshop or Adobe InDesign or something else. In any case, the PDF isn't the original file: get that and edit it.