Please help me with this, I received a drawing  to make some changes, but the drawing is defragmented, I can't do nothing because inclusive the letters are lines , the curves are a serial of lines , I will appreciate any help  to reverse this condition to access to make the changes that the drawing need

The drawing was probably imported from a PLT file (intentionally crippled). I am afraid you cannot reverse that.

My opinion is a PDF file was converted to a DWG file via a third party application in order to be able to edit it in AutoCAD.  Not all PDF to DWG file converters produce good results.  Most free versions produce virtual garbage in which case you would have been better off if you just used PDFAttach and traced over the image.  I don't believe this was intentional.  Somebody thought it was worth doing but as it turns out it just created more work and more headaches.  Call the person you got the file from and ask them to send you the PDF instead.  Bring it into AutoCAD and trace over it.

... and don't forget the obvious:  ask the sender if they have the file in its original drawing (.dwg .dgn or other) format, and if they do to send *that* to you!  Somewhere the original exists.Dave

Thank you all, occurred as John says, the original file is in PDF, unfortunately the original DWG file was lost and only had that, either way I have to work longer drawing.

I hate the PDF file format.  It was never intended to be used as a substitute for CAD drawings.