Why are Bitmap-Fonts used automatically?

The standard Computer Modern fonts are in OT1 encoding, so when you request T1 font encoding bitmap fonts are used. Install the package cm-super to get Computer Modern fonts with T1 support.

There's no change in your document needed. Just install cm-super using the MiKTeX Package Manager or the TeX Live Manager. The package manager will update the font map files for you. Then recompile.

• cm-super MiKTeX package information
• Installing with TeX Live
• cm-super for download on CTAN

• Debian package, works on Debian and Ubuntu for example with

  sudo apt-get install cm-super
  

While this is a solution for fixing the default look, consider using a T1 supporting font, such as Latin Modern, which has been designed as successor to Computer Modern and thus is very similar but intended to be better. For the decision, this may help:

• Latin Modern vs. cm-super

And for trying yourself, just add:

\usepackage{lmodern}

The default fonts for T1 are bitmaps, as has been mentioned, and the most straightforward solution is to use cm-super, like Stefan said. Alternatively, you could use the Latin Modern fonts (package lmodern). It is based on Computer Modern and supports a lot of languages written in the Latin alphabet.

Use

\usepackage[T1]{fontenc}
\usepackage{ae,aecompl}

Both cm-super and lmodern used look worse than the real type 1 Computer Modern fonts (depending on your PDF viewer, zoom level, etc.). The ae package is an ugly kludge, but at least it looks ok, and you will get vectors instead of bitmaps. Copy-paste is another story...