Improve documentation around barcodes, re-organize configuration and update links

docs/advanced_usage.md

@@ -507,3 +507,43 @@ existing tables) with:
     Using mariadb version 10.4+ is recommended. Using the `utf8mb3` character set on
     an older system may fix issues that can arise while setting up Paperless-ngx but
     `utf8mb3` can cause issues with consumption (where `utf8mb4` does not).
+
+## Barcodes {#barcodes}
+
+Paperless is able to utilize barcodes for automatically preforming some tasks.
+
+At this time, the library utilized for detection of bacodes supports the following types:
+
+- AN-13/UPC-A
+- UPC-E
+- EAN-8
+- Code 128
+- Code 93
+- Code 39
+- Codabar
+- Interleaved 2 of 5
+- QR Code
+- SQ Code
+
+You may check for updates on the [zbar library homepage](https://github.com/mchehab/zbar).
+For usage in Paperless, the type of barcode does not matter, only the contents of it.
+
+For how to enable barcode usage, see [the configuration](/configuration#barcodes).
+The two settings may be enabled independently, but do have interactions as explained
+below.
+
+### Document Splitting
+
+When enabled, Paperless will look for a barcode with the configured value and create a new document
+starting from the next page. The page with the barcode on it will _not_ be retained. It
+is expected to be a page existing only for triggering the split.
+
+### Archive Serial Number Assignment
+
+When enabled, the value of the barcode (as an integer) will be used to set the document's
+archive serial number, allowing quick reference back to the original, paper document.
+
+If document splitting via barcode is also enabled, documents will be split when an ASN
+barcode is located. However, differing from the splitting, the page with the
+barcode _will_ be retained. This allows application of a barcode to any page, including
+one which holds data to keep in the document.