diff --git a/.github/workflows/manubot.yaml b/.github/workflows/manubot.yaml
index 9a7d5766..3d390d60 100644
--- a/.github/workflows/manubot.yaml
+++ b/.github/workflows/manubot.yaml
@@ -8,6 +8,17 @@ on:
     branches:
       - main
       - master
+  workflow_dispatch:
+    inputs:
+      BUILD_PDF:
+        description: generate PDF output (true or false)
+        default: "true"
+      BUILD_DOCX:
+        description: generate DOCX output (true or false)
+        default: "false"
+      BUILD_LATEX:
+        description: generate LaTeX output (true or false)
+        default: "false"
 jobs:
   manubot:
     name: Manubot
@@ -21,6 +32,12 @@ jobs:
         with:
           # fetch entire commit history to support get_rootstock_commit
           fetch-depth: 0
+      - name: Set Environment Variables (Workflow Dispatch)
+        if: github.event_name == 'workflow_dispatch'
+        run: |
+          echo "BUILD_PDF=${{ github.event.inputs.BUILD_PDF }}" >> $GITHUB_ENV
+          echo "BUILD_DOCX=${{ github.event.inputs.BUILD_DOCX }}" >> $GITHUB_ENV
+          echo "BUILD_LATEX=${{ github.event.inputs.BUILD_LATEX }}" >> $GITHUB_ENV
       - name: Set Environment Variables
         run: |
           TRIGGERING_SHA=${GITHUB_PULL_REQUEST_SHA:-$GITHUB_SHA}
diff --git a/build/build.sh b/build/build.sh
index 5cebfc59..778c9580 100755
--- a/build/build.sh
+++ b/build/build.sh
@@ -11,6 +11,16 @@ export TZ=Etc/UTC
 # Default Python to read/write text files using UTF-8 encoding
 export LC_ALL=en_US.UTF-8
 
+# Set option defaults
+CI="${CI:-false}"
+BUILD_PDF="${BUILD_PDF:-true}"
+BUILD_DOCX="${BUILD_DOCX:-false}"
+BUILD_LATEX="${BUILD_LATEX:-false}"
+SPELLCHECK="${SPELLCHECK:-false}"
+# Pandoc's configuration is specified via files of option defaults
+# located in the $PANDOC_DATA_DIR/defaults directory.
+PANDOC_DATA_DIR="${PANDOC_DATA_DIR:-build/pandoc}"
+
 # Generate reference information
 echo >&2 "Retrieving and processing reference metadata"
 manubot process \
@@ -20,10 +30,6 @@ manubot process \
   --skip-citations \
   --log-level=INFO
 
-# Pandoc's configuration is specified via files of option defaults
-# located in the $PANDOC_DATA_DIR/defaults directory.
-PANDOC_DATA_DIR="${PANDOC_DATA_DIR:-build/pandoc}"
-
 # Make output directory
 mkdir -p output
 
@@ -39,8 +45,9 @@ pandoc --verbose \
 DOCKER_RUNNING="$(docker info &> /dev/null && echo "yes" || true)"
 
 # Create PDF output (unless BUILD_PDF environment variable equals "false")
+# The double-commas (,,) lowercase the variable.
 # If Docker is not available, use WeasyPrint to create PDF
-if [ "${BUILD_PDF:-}" != "false" ] && [ -z "$DOCKER_RUNNING" ]; then
+if [ "${BUILD_PDF,,}" != "false" ] && [ -z "$DOCKER_RUNNING" ]; then
   echo >&2 "Exporting PDF manuscript using WeasyPrint"
   if [ -L images ]; then rm images; fi  # if images is a symlink, remove it
   ln -s content/images
@@ -53,9 +60,9 @@ if [ "${BUILD_PDF:-}" != "false" ] && [ -z "$DOCKER_RUNNING" ]; then
 fi
 
 # If Docker is available, use athenapdf to create PDF
-if [ "${BUILD_PDF:-}" != "false" ] && [ -n "$DOCKER_RUNNING" ]; then
+if [ "${BUILD_PDF,,}" != "false" ] && [ -n "$DOCKER_RUNNING" ]; then
   echo >&2 "Exporting PDF manuscript using Docker + Athena"
-  if [ "${CI:-}" = "true" ]; then
+  if [ "${CI,,}" = "true" ]; then
     # Incease --delay for CI builds to ensure the webpage fully renders, even when the CI server is under high load.
     # Local builds default to a shorter --delay to minimize runtime, assuming proper rendering is less crucial.
     MANUBOT_ATHENAPDF_DELAY="${MANUBOT_ATHENAPDF_DELAY:-5000}"
@@ -77,7 +84,7 @@ if [ "${BUILD_PDF:-}" != "false" ] && [ -n "$DOCKER_RUNNING" ]; then
 fi
 
 # Create DOCX output (if BUILD_DOCX environment variable equals "true")
-if [ "${BUILD_DOCX:-}" = "true" ]; then
+if [ "${BUILD_DOCX,,}" = "true" ]; then
   echo >&2 "Exporting Word Docx manuscript"
   pandoc --verbose \
     --data-dir="$PANDOC_DATA_DIR" \
@@ -86,7 +93,7 @@ if [ "${BUILD_DOCX:-}" = "true" ]; then
 fi
 
 # Create LaTeX output (if BUILD_LATEX environment variable equals "true")
-if [ "${BUILD_LATEX:-}" = "true" ]; then
+if [ "${BUILD_LATEX,,}" = "true" ]; then
   echo >&2 "Exporting LaTeX manuscript"
   pandoc \
     --data-dir="$PANDOC_DATA_DIR" \
@@ -95,7 +102,7 @@ if [ "${BUILD_LATEX:-}" = "true" ]; then
 fi
 
 # Spellcheck
-if [ "${SPELLCHECK:-}" = "true" ]; then
+if [ "${SPELLCHECK,,}" = "true" ]; then
   export ASPELL_CONF="add-extra-dicts $(pwd)/build/assets/custom-dictionary.txt; ignore-case true"
 
   # Identify and store spelling errors
diff --git a/build/environment.yml b/build/environment.yml
index 40abf49e..8cac4276 100644
--- a/build/environment.yml
+++ b/build/environment.yml
@@ -20,7 +20,7 @@ dependencies:
   - yamllint=1.25.0
   - pip:
     - errorhandler==2.0.1
-    - git+https://github.com/manubot/manubot@2c028a7a87be24a76e2dec3ac7db6e8754ae6d4a
+    - git+https://github.com/manubot/manubot@2fc85b57be896c6262398f343b550197127c0ccb
     - isbnlib==3.10.3
     - opentimestamps-client==0.7.0
     - opentimestamps==0.4.1