Looking for an extension that allow users to preview downloadable products

Hi, I write projects for high schools, colleges, masters, etc. I want to set up an opencart store where I can sell my previous/present projects/research work as downloadable files(pdf)

I understand that opencart supports this, however I am looking for an extension that would allow users to view/read some parts of each project(like the first chapter) even before they buy so that if they are impressed, they can then pay and download the full files.. .

Any suggestions please
Thanks

well, just create a PDF file, to be linked and so downloadable on the Product Page itselfs,
containing, what you like to publish for free. And another PDF File, or something else zipped,
containing the Full Content, would be 'acting as' Product, and downloadable, after payment has
been received, the OC regular way.
And just make sure, to use a Mod, able to place an individual Link on every Product Page,
I did not check, if all Mod's, listed below, will be able to !
Good Luck!
Ernie

Some ways, to create such Product Page Links, and it also depends on the THEME used,
if such a link works and how it looks like on screen.
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Opencart 2 Public Product Downloads free OC v.2.3.x
https://www.opencart.com/index.php?rout ... n_id=28301
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Custom text on product pages free OC v.2.x
https://www.opencart.com/index.php?rout ... n_id=27633
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Product Extra Field free OC v.2.x
https://www.opencart.com/index.php?rout ... n_id=27794
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Custom Link in Products free OC v.1.5.6.x
https://www.opencart.com/index.php?rout ... n_id=21139
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Links on product page paid:
https://www.opencart.com/index.php?rout ... n_id=23824
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