The aside (in parens) is an interruption, and it can be rearranged to avoid that interruption:

Packages can be installed from media like <acronym>DVD</acronym> disks or images.

This whole sentence contains several different ideas which should be split up.

• packages can be installed from media
• a network connection is then not needed
• the packages might be older or outdated

This seems overly specific. We can probably just say that the media must be mounted.

"Not" looks wrong.

A lot of these sentences are if/then, with a pause between the two. These are somewhat halting to read. Try to use sentences without those pauses:

<command>pkg</command> can be used normally as long as REPOS_DIR is set.

Please avoid contractions: https://www.freebsd.org/doc/en_US.ISO8859-1/books/fdp-primer/writing-style-guidelines.html

Sorry, it is hard to understand what this means.

There should be some type of conclusion at the end of this.

Not really, because repository configuration file on DVD has /dist path hardcoded. I think it needs an explanation instead of that (or why) this specific path is required.

"though" would have commas around it, but can better be removed. Also s/may/might/, and "it should be noted" is not really needed at all. So:

Only a subset of packages are available this way, and those packages might be outdated.

Again, this is an if/then sentence with a pause in the middle. Two of them, really. (Ignoring wrapping...)

Media to be used as a local package repository must be mounted on <filename>/dist</filename>.

The second sentence that explains why /dist must be used does not really explain why. Where is it hardcoded?

This example should be preceded by a sentence that explains that this example shows mounting a DVD containing pacakges. It should also point out that on this DVD, those packages are in the root, as opposed to wherever they are on an install DVD.

Another if/then sentence with a pause. How about

Set <envar>REPOS_DIR</envar> to ... to point &man.pkg.1; to the new package repository.

or

Point &man.pkg.1; to the new repository by setting <envar>REPOS_DIR<envar> to ...

Not sure how this interacts with the requirement of /dist.

Needs an article here ("the"), but it's also not clear.

The meaning of "bootstrapped" here might not be clear, but otherwise very nice!