PDF files not Opening in “Document Viewer” - in Ubuntu 20.04.2.0

What is the output of:

file /media/navin/WIN-7\ New250GB/Documents\ and\ Settings/mayur/Desktop/Engg\ Design\ Seminar\ June-Aug\.\ 2007/EDS\ Material\ CD/Compressors.pdf

Please?

The output is as under:
-------------------------------------------------------------------------------------------------------------------------------------------------------------------
navin@linux:~$ file /media/navin/WIN-7\ New250GB/Documents\ and\ Settings/mayur/Desktop/Engg\ Design\ Seminar\ June-Aug\.\ 2007/EDS\ Material\ CD/Compressors.pdf
/media/navin/WIN-7 New250GB/Documents and Settings/mayur/Desktop/Engg Design Seminar June-Aug. 2007/EDS Material CD/Compressors.pdf: cannot open `/media/navin/WIN-7 New250GB/Documents and Settings/mayur/Desktop/Engg Design Seminar June-Aug. 2007/EDS Material CD/Compressors.pdf' (No such file or directory)
navin@linux:~$
--------------------------------------------------------------------------------------------------------------------------------------------------------------------

It seems that the path to that file is too complicated for an error-free retyping.

I suggest that you use the file manager program to copy that file into your home directory, and then simply issue the command

file Compressors.pdf
head --bytes=100 Compressors.pdf

The captioned folder "Engg Design Seminar June-Aug. 2007" copied into home directory.
Then issued above TWO commands. Output is as under:

-----------------------OUT PUT----------------------------------
avin@linux:~$ file Compressors.pdf
Compressors.pdf: cannot open `Compressors.pdf' (No such file or directory)
navin@linux:~$ head --bytes=100 Compressors.pdf
head: cannot open 'Compressors.pdf' for reading: No such file or directory
navin@linux:~$
----------------------------END-----------------------------------------

Does this require some package installation?
How to proceed further?

You'll need to provide the full path to the file or use the cd command (like you do in Windows) to change to the containing directory, then you can run commands. You were told there was no such file because the path that you were in, in the terminal is not the one containing your filem

My recommendation was to copy just a single file to your home directory. If you copy the whole directory tree, then this is fine but needs slightly different actions.

I suggest:

Open a terminal window
start typing "cd Engg" and then press the Tab key.
This should add the rest of the directory name.
Then press the enter key.
start typing "cd EDS" and then press the Tab key.
This should add the rest of the directory name.
Then press the enter key.
Next: issue the two commands

file Compressors.pdf
head --bytes=100 Compressors.pdf

and finally copy/paste all output into this question document that we can check.

Thank you sir for further clarity to me.
The output as per #6 is as under:
----------------------------- OUT PUT-------------------------
navin@linux:~$ cd Engg\ Design\ Seminar\ June-Aug.\ 2007/
navin@linux:~/Engg Design Seminar June-Aug. 2007$ cd EDS\ Material\ CD/
navin@linux:~/Engg Design Seminar June-Aug. 2007/EDS Material CD$ file Compressors.pdf
Compressors.pdf: data
navin@linux:~/Engg Design Seminar June-Aug. 2007/EDS Material CD$ head --bytes=100 Compressors.pdf
�2C^t��XD���gF
              2�TE��[��s��
                          xLY��n�<�5N0u���S��� {-�Lb>Uב:&���t_��Mڶ&�r�R*
navin@linux:~/Engg Design Seminar June-Aug. 2007/EDS Material CD$
-------------------------------END--------------------------------

The file contents are not what a PDF (portable document format) file should be.
The first bytes of a PDF file have to be "%PDF", and this is not the case with your file.

It seems that something went wrong with the files.
Do you still have the original CD?

yes

I suggest that you try copying the files from the CD again, if possible.

Yes, I have again copie3d the CD on the desktop and named it as "EDS Material CD"

Can the files now be opened, or - if not - what is the output of the "head ..." command on one of these files?

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