Is Eagle PCB design software easy to use?

First of all, if you are using Proteus then you can export your PCB design as Gerber file, may be you are using very old version. Also in trial version you would not be able to do it.

Secondly if you are a beginner then Eagle or Orcad might be difficult for you, they have steep learing curve and specially designed for the professionals.

There are many other easier PCB designing softwares, but for a beginner I will recommend EasyEDA and Fritzing, they both are free, easy to use and available in both offline and online version. I suggest you to use online, it have lot of features. Further you can find many articles on internet to find and compare PCB softwares, one such article is available on this website itself How to Choose The Best PCB Design Software

I am also a big fan of EasyEDA, they have very goof user community so you can find symbols and footprints for almost any component. Also since it is cloud based and free software I do not find any reason not to use it. 

Yeah Easy EDA is good and it also a auto-rout feature which is awesome. 

But KiCAD is also very good and it has a 3D option which you can use to visualize your PCB board in 3D model. This helps you realize your product much more easier especially while designing your casings.

This feature has always helped me to impress my clients. Sticking on to the question Eagle is a paid version and is also very good. It also has this 3D export option and a good collection of libraries. Also it is universal hence you will not face any problem while exporting your designs 

Eagle gets much popularity from hundreds of thousands of engineers, makers, students and even hobbyists in open source hardware communities due to its powerful yet easy-to-use functions.

However, there are also some other powerful PCB design software for beginners. To name a few:

DipTrace is popular and budget friendly PCB design software package with a fairly robust set of features. It's easy to learn and available in a free, albeit limited, version and has very reasonable pricing for its unlimited version. It is well suited to hobbyist and those new to the creation of PCBs.

PCB Wizard is a powerful PCB design suite that allows users to create single and dual sided PCB designs. It is perfect for hobbyists and those are that just starting out in the field of PCB design. Offered as freeware, it further lends itself to non-professional users.

You may find a further PCB design software survey here.