diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index b92963c78e0a4322db1730b650d2a00310f4243d..3e08ef883c14a533ac3ec2aff948c975f8e6aa39 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -6,6 +6,10 @@ For a detailed view of what's changed, refer to the {url-repo}/commits[commit hi
 
 == Unreleased
 
+=== Added
+
+* add private key on scan entry to set private property on scanned file (#51)
+
 === Fixed
 
 * apply camelCase transformation to keys in scanned component version descriptor (antora.yml) (#49)
diff --git a/docs/collector-extension/modules/ROOT/pages/configure-scan.adoc b/docs/collector-extension/modules/ROOT/pages/configure-scan.adoc
index bc8b1a117f30d7f4e691662fdb23223f4efc93c0..ffe6c5cd3d46fa2aadebe2ed65324ddb30b7f290 100644
--- a/docs/collector-extension/modules/ROOT/pages/configure-scan.adoc
+++ b/docs/collector-extension/modules/ROOT/pages/configure-scan.adoc
@@ -100,6 +100,11 @@ Acceptable keys for the map value are listed in the table below.
 |false
 |Boolean
 |Whether to clean the scan directory before running commands.
+
+|<<private-key,private>>
+|undefined
+|Boolean
+|Sets the value of the private property on all files scanned by this action.
 |===
 
 {empty}* required
@@ -246,3 +251,21 @@ In this case, the Collector instance will be recycling a worktree it has used on
 If Collector creates a new worktree in which to run the Collector instance, there's usually no need to clean.
 However, if the Collector instance has multiple steps, and those steps generate files into the same scan directory, it may be necessary to clean the scan directory at the start of each step.
 You'll need to put some thought into when you want the scan directory to be cleaned.
+
+== private key
+
+NOTE: Use of this key requires Antora 3.2.0 or better.
+
+By default, Antora will import underscore files (i.e., files that either start with an underscore or are found inside a directory that starts with an underscore), but will not publish those files.
+This behavior can be overridden using the `private` key.
+
+If the `private` key is set on the entry, the value of that key will be propagated to the `private` property on the scanned (or updated) file.
+This property, in turn, controls whether the file is published, assuming the file is in a publishable family.
+If this property is not set, the default behavior in Antora takes effect.
+
+By setting the `private` key to `true`, you can force Antora to publish an underscore file.
+Conversely, by setting the `private` key to `false`, you force Antora to not publish the file, even if it's in a publishable family.
+
+Note that all such files are still imported into the content catalog by Antora.
+This key is merely controlling which publishable files actually get published to the site.
+An unpublishable file can still be used in an include directive.
diff --git a/packages/collector-extension/lib/index.js b/packages/collector-extension/lib/index.js
index 7280a210007a9041bc73836d196e39adbb3afdd9..1485bc04e5b41e28bdb8d59cfa7fb58edf0f1b19 100644
--- a/packages/collector-extension/lib/index.js
+++ b/packages/collector-extension/lib/index.js
@@ -154,7 +154,7 @@ module.exports.register = function ({ config: { createWorktrees = 'auto', keepWo
               }
             }
           }
-          for (const { dir, files, into } of scans) {
+          for (const { dir, files, into, private: private_ } of scans) {
             let componentVersionDesc
             const scannedFiles = await srcFs(dir, files, into.dir).then((result) =>
               result.filter((file) => (file.path === 'antora.yml' ? !(componentVersionDesc = file) : true))
@@ -190,6 +190,7 @@ module.exports.register = function ({ config: { createWorktrees = 'auto', keepWo
             for (const file of scannedFiles) {
               const relpath = file.path
               const existingFile = targetFiles.find((it) => it.path === relpath)
+              if (private_ != null) Object.assign(existingFile || file, { private: private_ })
               if (existingFile) {
                 Object.assign(existingFile, { contents: file.contents, stat: file.stat })
               } else {
diff --git a/packages/collector-extension/test/extension-test.js b/packages/collector-extension/test/extension-test.js
index 56ead32e5559f220f9bca5119de139ceda7a3e65..0ad97d5489aeeb6169a63abde7b2597c37a0e377 100644
--- a/packages/collector-extension/test/extension-test.js
+++ b/packages/collector-extension/test/extension-test.js
@@ -1011,6 +1011,48 @@ describe(localPackageName, () => {
       })
     })
 
+    it('should label files as private if private key is true on scan entry', async () => {
+      const collectorConfig = {
+        scan: { dir: 'other-docs', private: true },
+      }
+      await runScenario({
+        repoName: 'at-start-path',
+        startPath: 'docs',
+        collectorConfig,
+        pre: (contentAggregate) => {
+          assert.equal(contentAggregate.length, 1)
+          assertx.empty(contentAggregate[0].files)
+        },
+        post: (contentAggregate) => {
+          assert.equal(contentAggregate[0].files.length, 1)
+          assert.equal(contentAggregate[0].files[0].private, true)
+        },
+      })
+    })
+
+    it('should label files as not private if private key is false on scan entry', async () => {
+      const collectorConfig = {
+        scan: { dir: 'with-underscore-files', private: false },
+      }
+      await runScenario({
+        repoName: 'at-start-path',
+        startPath: 'docs',
+        collectorConfig,
+        pre: (contentAggregate) => {
+          assert.equal(contentAggregate.length, 1)
+          assertx.empty(contentAggregate[0].files)
+        },
+        post: (contentAggregate) => {
+          assert.equal(contentAggregate[0].files.length, 2)
+          assert.equal(contentAggregate[0].files[0].private, false)
+          assert.equal(contentAggregate[0].files[1].private, false)
+          const underscoreFile = contentAggregate[0].files.find((it) => it.src.basename.charAt() === '_')
+          assert(underscoreFile != null)
+          assert.equal(underscoreFile.src.basename, '_bar.adoc')
+        },
+      })
+    })
+
     it('should not fail if scan dir does not exist', async () => {
       const collectorConfig = {
         scan: { dir: 'does-not-exist' },
diff --git a/packages/collector-extension/test/fixtures/extension-test/at-start-path/with-underscore-files/modules/ROOT/pages/_bar.adoc b/packages/collector-extension/test/fixtures/extension-test/at-start-path/with-underscore-files/modules/ROOT/pages/_bar.adoc
new file mode 100644
index 0000000000000000000000000000000000000000..6e5fa2e36354c48a8b43226123d6c6e36e1010b1
--- /dev/null
+++ b/packages/collector-extension/test/fixtures/extension-test/at-start-path/with-underscore-files/modules/ROOT/pages/_bar.adoc
@@ -0,0 +1,3 @@
+= Bar
+
+bar content
diff --git a/packages/collector-extension/test/fixtures/extension-test/at-start-path/with-underscore-files/modules/ROOT/pages/foo.adoc b/packages/collector-extension/test/fixtures/extension-test/at-start-path/with-underscore-files/modules/ROOT/pages/foo.adoc
new file mode 100644
index 0000000000000000000000000000000000000000..41381f2e8b98b94d7d5f08e7324d45d3aaeab724
--- /dev/null
+++ b/packages/collector-extension/test/fixtures/extension-test/at-start-path/with-underscore-files/modules/ROOT/pages/foo.adoc
@@ -0,0 +1,3 @@
+= Foo
+
+include::_bar.adoc[lines=3..]