I have ubuntu 12.04. I want to change permissions on all folders and files at the same time so that anyone can modify or remove them.
If you are talking about your home folder or any shared folder then you can
chmod -R 777 /Your/folder/path/. If you just want to make the files read and write enabled then I would set the permissions to 766 instead.
This said, for this to work, your partition entry in the fstab file must permit read/write and execute permissions.
First important point you do not want to change the permissions on all files and folders: changing the permissions on some files can break your system.
Command Line Way
So lets assume instead you want to change the the permissions in all the files in a particular folder and its sub-folders.
I have a folder in my home directory which does not give any access to "others"; this contains a sub-folder sub which also does not give any access to others.
If I now want to give "others" read access I make sure I am in the correct directory and enter
chmod -R o+r *
As you can see the permissions are changed
If you only want to do this in the current directory omit
-R from the command.
If you want to do this in a directory you don't own you will need to prefix the command with
If the files are owned by you run the file manager if not press ALT+F2
gksu nautilus and enter your password when requested.
Hold down the SHIFT key or CTRL key to select the files you want: SHIFT selects all the files in a range CTRL selects one file at a time. Now right click and select properties; in the window that opens you can select the permissions tab and you can set the permissions from there.