Agreed to zacharee1 answer , but still if you can't find pdf option just press alt and write pdf , you would be shown an option export to pdf
if you don't know how to do something , just press the alt key , write that something and below would be the options , click on it.
**If you still can't get it , update the question , there are many alternatives to do the above and if you think , your problem would be solved by microsoft word then do the below steps
**
steps to install microsoft office in ubuntu :
- press ctrl + alt + t
- type
sudo apt-get install wine
- enter the password, no letters would be shown , but enter the correct password
- press enter
- Download Microsoft Office from the website
- after downloading the office , right click on setup.exe
- open with -> other application
- select wine, (if you can't find wine , then click on the view all application button and then scroll and find wine
- press ok
- install microsoft office next -> next -....->finish
- insert your images in word
- go to file , export and convert to pdf
- although this procedure is long but you can run any windows program in ubuntu