uiputfile just creates a full path for downloading file in server side, so you need to execute writetable (for .csv and .xlsx) and copyfile (for other file formats).
Here is a sample to download a PDF file from Web App.
[file,path] = uiputfile('test.pdf');
if isequal(file,0) || isequal(path,0)
disp('User clicked Cancel.')
else
str = which('test.pdf', '-all');
if ~isempty(str)
copyfile(str{1}, fullfile(path, file))
end
end
