Its latest version is AutoCAD 2018, which has enhanced following features.

• PDF import : Import geometry, including SHX font files, fills, raster images, and TrueType text into a drawing from a PDF
• External file references: Save time and minimize frustration with tools to fix broken paths for externally referenced files.
• Object selection: Selected objects stay in the selection set, even if you pan or zoom off screen.
• Text to Mtext: Convert combinations of text and Mtext objects to a single Mtext object.
• User interface: Work intuitively with common dialog boxes and toolbars.
• Share design views: Publishes design views of your drawing to a secure location for viewing and sharing in a web browser.
• High-resolution monitor support: Enjoy the best possible viewing experience ever, even on 4K and higher resolution displays.
• AutoCAD mobile app: View, create, edit, and share CAD drawings on your mobile device with the AutoCAD mobile app

AutoCAD is very expensive and there are number of other CAD software available at comparatively much lesser prices but performing functions are not similar to AutoCAD.

SketchUp is a great tool for quickly visualizing an interior design project. Ed Cotey shows you how to develop a floor plan quickly, using an imported AutoCAD file and a number of SketchUp tools to build the walls, insert doors and windows, create and use materials, and apply special effects such as styles and shadows. Plus, learn to set up scenes for use in client presentations.

AutoCAD:

• Best for Drafting
• Easy to use 2D, 3D is tough for advance drawings.
• Basic CAD tool
• Has precision upto 10 decimal places
• More Theoretical oriented.

SolidWorks:

• Best for 2D and Basic 3D
• Easy to work in 3D rather than 2D
• High end CAD tool
• More Practical oriented.

 If you learn AutoCAD before Revit, you’re going to end up with all the bad habits AutoCAD drafters have, that don’t work on Revit.

Revit is a whole different mindset from AutoCAD, in part because it’s 3D, in part because you’re building a model (not just a drawing), and in part because there’s a whole lot of information attached to each and every element you model.

Learn Revit. And then if you need to, learn AutoCAD.

 new features of AutoCAD 2017

Autodesk Desktop app:

The new Autodesk desktop app is added in the latest release of AutoCAD where you can manage software updates, watch latest videos and articles for learning software skills, access forums and Autodesk knowledge network. You can also use Autodesk desktop app for sending feedback to Autodesk and accessing online AutoCAD help.

PDF to DWG:

This is probably the most awaited feature in AutoCAD, starting with AutoCAD 2017 you can import drawings from PDF format to AutoCAD as geometry and text objects.

Making centerline and center marks:

With new AutoCAD 2017, you can easily add center lines and center marks to the geometry. Simply type the command CENTERMARK and click on the circular object to create the center mark. You can use this command to make a center mark on circle, arc and fillet.

Migrate custom settings:

The new custom settings migration setting window is more visually appealing and has easy to understand interface.

Enhanced graphics:

With new AutoCAD, you will see an enhanced graphics in 2D and 3D with improved performance and smooth visible features.

For a more comprehensive list of AutoCAD 2017 enhancements see this article of Autodesk blog.

CNC stands for Computer Numerical Control…which in todays context means the controlling of machine tools by computer. The old days of one man standing in front of a lathe or a mill or a welder are almost gone. Today..material (plastics, steels, etc etc) are loaded into a machine tool and the program is run..and it removes, drills and welds the parts into something useful. Ballpoint pen tips…care to stand there for 10 hrs a day making those little buggers? Nope.  lengths of metal are fed into the machines..the program is run..and it kicks out thousand of them. Lug nuts, engine parts, nuts and bolts for aerospace applications, jet engine parts and so on and so forth. Now days..one person can run 3-5 machines by him/herself, and make thousands of parts per day. In the “old days”..one person might make a couple hundred. Which makes those parts cheaper once the personel costs are lowered. In the “good old days” one had to be a machinist to operate and accurately make “parts”. Today..one can pull a barely educated person off the street and have them making perfect parts in less than an hour in many cases. All they have to do is feed the machine and hit the Cycle Start button..and empty the machine of new parts the machine just made.  Which of course means there are far far fewer job openings in manufacturing..compounded by the fact one can train a tribesman in the Congo to make those very same parts for a lot cheaper than an American worker can. We get good parts at the cost of American jobs…Im still trying to figure out of this is a good thing..or a bad thing.

Autocad  is pretty good software, it hardly seems fair to blame the software for what will almost certainly turn out to be UIE (user induced error).
ReMark is right, no shortage of folks willing to help here on the forum.
Try using the FLATTEN command before trying to join them, perhaps that will help.
If you were having difficulty with JOIN in the PEDIT command, make sure that when you see the FUZZ DISTANCE prompt you hit ENTER, so that the command will complete.
If you ignore that and ESCAPE, they will not be joined.

AutoCAD 2010 (and higher) can directly read in files in the PDF format – it imports them as underlays. The contents of PDF files is not converted to AutoCAD entities, but it is displayed as an underlay (xref). You can use osnaps to snap the drawed or edited AutoCAD objects to the lines in PDF files.

The underlay (PDF, DWF or DGN) behaves the same as other external references (xrefs) in the DWG format. To attach a PDFunderlay, you can use the PDFATTACH command or the more general ATTACH command.

During the command you can choose specific page(s) in multipage PDF files, the scale, rotation and the insertion point (lower left). If the PDF file is updated, also its contents in AutoCAD is updated.