To elaborate the question further, is it possible to load the images / pdf files to a VSAM file thru a COBOL program
Yes, of course -- data is data is data is data. Note, however, that PDF files are frequently larger (much larger) than the typical 32760-byte record length limit of the mainframe, so your program will have to work out a way to split the PDF file into some number of records.
how to read images, pdf files thru the COBOL program
With a READ statement in COBOL -- just like any other data. PDF file data is nothing but data to COBOL.
read / write images / pdf files into VSAM files are available to view?
THAT's not going to happen -- a PDF file can be handled as an image on the mainframe through Unix System Services (I use them on my internal HTML pages at my site), but as far as I know there is no PDF viewer available for COBOL on z/OS. And since you would need a graphics device -- not the 3270 emulator software usually used to connect to the mainframe -- to even view the PDF file, there would be many, many, MANY issues in even attempting to view a PDF with a mainframe program.