A text area would be the way to go, as it will show a scroll bar and wrap text if the content of the textfile is larger than the space available. Just make sure that you make it non-editable in App Designer (Inspector > Interactivity) if you only want to show the text but not allow the user to edit it.
I suppose you have one textfile per person. In this case, the callback for the dropdown menu could look similar to this:
value = app.DropDown.Value;
% choose the correct textfile depending on which person was selected
switch value
case 'Option 1'
myfile = 'person1.txt';
case 'Option 2'
...
end
% open the file and display its contents in the text area
fileID = fopen(myfile);
C = textscan(fileID, '%s', 'Delimiter', '\n');
app.TextArea.Value = C{1};
fclose(fileID);
To get to the callback, right-click on the dropdown menu and select Callbacks > DropDownValueChanged callback.
Note that you will have to adjust the callback code if you change the names of the options in the dropdown menu (Option 1, Option 2, etc.).
