PDF Reader
 

I have used FOXIT reader in windows 10 and like it to turn a ,doc into a .PDF. What simple app could I use in Linux? Would be nice if I could also update the PDF file (optional). My problem I am not familiar with the Linux lingo. Please keep the answer simple and clear. Thanks, Fred

Libreoffice can save a .DOC to a PDF. Many Linux programs (including the Chrome web browser), can print to PDF files. You can even use libreoffice from the command line to batch convert .DOC files to .PDF's. There are many choices for editors too: please see the "Question Guidelines" link in my posting signature. A brief Google search for "linux pdf editors" will yield lots, such as this list from December 2017:
https://itsfoss.com/pdf-editors-linux/
You've been a member here for two years now, what 'lingo' do you mean? And when asking volunteers for help, it's not very good to tell people what kind of answers you'll accept.

I can not see how to make Libreoffice convert a .doc to a .PDF. Tried "Save as". Lingo example is: Terminal language. I basically do Internet, word processing and emails. I use Linux because it is reliable. Thanks, Fred

The print dialog box from whatever desktop application you are running should have a print to file option where you can typically select PDF or PS (PostScript). In addition you should also be able to enter the desired file name as well as save to folder.

In most open-source apps you have save as for saving projects, you use export/export for what you want to do.

BTW My LibreOffice has a export as pdf button on the toolbar.

And a menu entry.

You can get Foxit for Linux, too.
https://www.foxitsoftware.com/pdf-reader/