PDF2XLS

PDF2XLS converts PDF invoices into rows in a Google Spreadsheet. It supports three independent extraction workflows that you can switch between via configuration. Optionally it can upload the original PDF to a public location and write the link to the spreadsheet.

The APIs are not perfect — always double-check the output and fix errors manually.

Available workflows

You choose the workflow with the PreferredAPI setting in appsettings.json. Valid values:

PreferredAPI value	What it does	External services required
NuDelta	Sends the PDF to the NuDelta Invoice service and polls until extraction is done.	NuDelta Invoice account
OpenAIResponses	Sends the PDF as an input_file to the OpenAI Responses API with a structured prompt + JSON schema.	OpenAI account with API key
AzureDocumentIntelligence	Sends the PDF to the Azure Document Intelligence prebuilt-invoice model and maps the structured fields to the internal schema.	Azure subscription with a Document Intelligence resource

All three workflows share the Google Sheets, Seq, and (optional) PDF upload configuration described below.

The application validates that the configuration fields required by the selected workflow are present at startup and exits with a clear error message if anything is missing.

---

Prerequisites

Regardless of which workflow you use, you always need:

• A Google Service Account with access to your target spreadsheet (JSON key file).
• A Google Spreadsheet with column headers matching the Mappings values.
• (Optional) A Seq server if you want centralised logs.
• (Optional) The PDF2URL helper executable if you want to upload PDFs and store a link in the sheet.

Then, depending on the workflow:

• NuDelta workflow → NuDelta Invoice account.
• OpenAIResponses workflow → OpenAI account with a funded API key.
• AzureDocumentIntelligence workflow → Azure subscription with a Document Intelligence (Form Recognizer) resource.

---

Account setup — how to obtain the parameters

1. Google Sheets (required for every workflow)

1. Go to https://console.cloud.google.com/ and create (or select) a project.
2. Open APIs & Services → Library and enable Google Sheets API.
3. Open APIs & Services → Credentials → Create Credentials → Service Account. Give it a name (this name becomes GoogleSheets:ApplicationName).
4. Open the new service account, go to the Keys tab, Add Key → Create new key → JSON. Save the downloaded file somewhere safe — the path goes into GoogleSheets:ServiceAccountFile.
5. Open the JSON file and copy the client_email value (looks like name@project.iam.gserviceaccount.com). In your Google Spreadsheet, click Share and grant Editor access to that email.
6. From the spreadsheet URL https://docs.google.com/spreadsheets/d/<SPREADSHEET_ID>/edit#gid=0, copy <SPREADSHEET_ID> into GoogleSheets:SpreadsheetId.
7. Set GoogleSheets:SheetName to the tab name (e.g. Sheet1).
8. Fill in GoogleSheets:Mappings — each field's value is the column letter in the sheet where that field should be written (e.g. "InvoiceNumber": "A"). Leave blank to skip a field.

2. NuDelta workflow

NuDelta Invoice account

1. Sign up at the NuDelta Invoice portal and confirm you have an active subscription.
2. Put your portal login into NuDeltaCredentials:Username and NuDeltaCredentials:Password. These are used with HTTP Basic auth against the NuDelta API.

3. OpenAIResponses workflow

1. Create an account at https://platform.openai.com/.
2. Add credit / payment method under Billing. The Responses API with input_file requires a funded account.
3. Go to API keys → Create new secret key. Copy the value (sk-…) into OpenAI:OpenAI_APIKey. You won't be able to see it again — store it safely.
4. Choose a model that supports the input_file content type and set it in OpenAI:OpenAI_Model. Recommended: gpt-4o-mini (good cost/quality trade-off). Other supported options at the time of writing: gpt-4o, gpt-4.1, gpt-4.1-mini.
5. Leave OpenAI:Prompt at the default unless you know what you're doing. The placeholder {schema} is substituted at runtime with the JSON schema the program expects — do not remove it.

Cost note: each invoice costs a few cents on gpt-4o-mini. Larger / multi-page PDFs cost more because the file is sent as base64.

4. AzureDocumentIntelligence workflow

1. In the Azure Portal, click Create a resource → AI + Machine Learning → Document Intelligence (previously called Form Recognizer).
2. Choose a subscription, a resource group, a region (e.g. westeurope), and a pricing tier. F0 (free) lets you process 500 pages/month; S0 (standard) is pay-as-you-go.
3. After deployment, open the resource and go to Keys and Endpoint in the left menu.
4. Copy Endpoint (looks like https://<resource>.cognitiveservices.azure.com/) into AzureDocumentIntelligence:Endpoint.
5. Copy KEY 1 into AzureDocumentIntelligence:ApiKey.
6. This workflow uses the prebuilt-invoice model, which is built into the service — you do not need to train anything. It is available in all regions that support Document Intelligence v4.

Note: Document Intelligence is deterministic and returns structured fields directly. It does not use OpenAI.

5. Optional: PDF upload to a public URL

If you want a DocumentLink column in the sheet pointing to the uploaded PDF:

1. Obtain or build a small uploader CLI (the PDF2URL helper) that takes a file path as an argument and prints the public URL to stdout.
2. Set UploadPDF:Enabled to "true" and UploadPDF:PDF2URLPath to the executable path.
3. Add DocumentLink to GoogleSheets:Mappings with the column letter to write the URL into.

Set UploadPDF:Enabled to "false" to skip uploading.

6. Optional: Seq logging

1. Run a Seq server (locally or remote).
2. Put its URL into Seq:ServerAddress (e.g. http://localhost:5341/).
3. Seq:AppName is the value of the App property used to filter events in Seq.

If you don't have a Seq server, leave the address empty — the file logs under logs/ still work.

---

Installation

1. Download the latest release and unpack it into a folder.
2. Open appsettings.json and fill in:
   • Always: PreferredAPI, GoogleSheets.*, DeleteFileAfterProcessing.
   • Workflow-specific (only for the workflow you chose — see above).
   • Optional: UploadPDF.*, Seq.*.

Full configuration reference

Section	Key	Required for	Description
(root)	PreferredAPI	All	NuDelta, OpenAIResponses, or AzureDocumentIntelligence.
(root)	DeleteFileAfterProcessing	All	"true" deletes the processed PDF; "false" keeps it.
NuDeltaCredentials	Username, Password	NuDelta	NuDelta portal credentials (HTTP Basic auth).
OpenAI	OpenAI_APIKey, OpenAI_Model, Prompt	OpenAIResponses	OpenAI key, model id, and prompt containing {schema}.
AzureDocumentIntelligence	Endpoint, ApiKey	AzureDocumentIntelligence	Azure Document Intelligence endpoint and key.
GoogleSheets	ServiceAccountFile, SpreadsheetId, ExpectedSpreadsheetName, SheetName, ApplicationName, Mappings	All	Google Sheets target. ExpectedSpreadsheetName is verified against the live spreadsheet title at startup; leave blank to skip the check. Mappings values are spreadsheet column letters.
UploadPDF	Enabled, PDF2URLPath	Optional	Enable to upload the PDF and store the link in DocumentLink.
Seq	ServerAddress, AppName	Optional	Centralised Seq logging.

---

Usage

This is a CLI application. Pass the path to the PDF invoice as the first argument, or drag-and-drop the PDF onto the executable.

PDF2XLS.exe "C:\invoices\invoice-001.pdf"

The selected workflow processes the file, parses the response into the internal schema, and appends a row to the configured Google Sheet.

Logging

On startup the program creates a logs/ subfolder next to the executable and writes a daily rolling log file (365 days retained). If Seq:ServerAddress is set, it also forwards events to Seq.

Processed file naming

When DeleteFileAfterProcessing is "false" and the Google Sheets write succeeds, the original PDF is renamed in-place using the following convention:

{RunTime} {RunID} {OriginalFileName}.bak

Part	Format	Details
RunTime	yyyyMMdd HHmmss	UTC timestamp of application start (UTC). Set once per batch run; all files in the same run share this value.
RunID	GUID	A unique ID generated for each file. Also written to the Google Sheet (column mapped to RunID).
OriginalFileName	—	The original filename, unchanged, including its extension.
.bak	—	Fixed suffix appended after the original extension.

All three parts are separated by a single space. There are no underscores in the filename.

Example:

20260517 013221 48070c04-bce5-4205-8ee7-ff506c8f2533 invoice-001.pdf.bak

Why spaces? Spaces make the three logical parts visually distinct without requiring a special delimiter character. The GUID already contains hyphens internally, so using an underscore as a separator would be ambiguous when splitting the name programmatically. Spaces allow a simple Split(' ', 3) to recover RunTime, RunID, and OriginalFileName unambiguously.

The file is left untouched if processing fails or the Google Sheets write does not succeed.

Notes per workflow

• NuDelta — polls for the result with exponential backoff (up to 5 attempts, 1-second base delay). The outer operation also retries on exception with a 1-second delay (up to 5 attempts).
• OpenAIResponses — the inner HTTP client retries on HTTP 429 / 5xx with exponential backoff (3 attempts). The outer operation also retries on exception with exponential backoff (3 attempts).
• AzureDocumentIntelligence — retries on exception with exponential backoff (3 attempts, 2 s → 4 s → 8 s). The Azure SDK additionally handles low-level transient HTTP errors.

---

Resilience — timeouts and retries

The application is designed so that a network outage or a service disruption during any stage of processing always leaves the source file untouched. The next run will pick it up and try again.

File-safety guarantee

A file is only renamed/deleted after all of the following have succeeded:

1. PDF extraction (NuDelta / OpenAI / Azure DI)
2. PDF upload to public URL (if UploadPDF:Enabled is "true")
3. Google Sheets row write

If any step fails — even after all retries are exhausted — the file stays in place.

Timeouts

Layer	Timeout	Behaviour on expiry
Azure DI polling	5 minutes	OperationCanceledException thrown; retried by outer policy (up to 3×)
NuDelta HTTP client (upload + poll requests)	5 minutes per request	TaskCanceledException thrown; propagates to outer retry policy
OpenAI HTTP client	5 minutes per request	TaskCanceledException thrown; propagates to outer retry policy
Google Sheets API calls (all three calls per write)	5 minutes per call	OperationCanceledException thrown; propagates as a write failure — file stays
PDF2URL process	5 minutes	Process is killed; empty URL returned → write not attempted → file stays

Retry policies

Workflow / stage	Retries	Delay strategy	What triggers a retry
NuDelta outer (whole operation)	up to 5	1 s fixed	Any exception except OperationCanceledException
NuDelta inner (result polling)	up to 5	Exponential (2^n s)	Document state is not done
OpenAI outer (whole operation)	up to 3	Exponential (2^n s)	Any exception except OperationCanceledException
OpenAI inner (HTTP call)	up to 3	Exponential (2^n s)	HTTP 5xx or HTTP 429
Azure DI (whole operation)	up to 3	Exponential (2^n s)	Any exception except OperationCanceledException
Google Sheets (each API call)	up to 3	Exponential (2^n s)	HTTP 5xx, HTTP 429, HttpRequestException, IOException

OperationCanceledException is never retried in any policy — it signals an intentional 5-minute timeout and should propagate immediately so the file is left untouched for the next run.

Spreadsheet name verification

Before processing any files the application fetches the spreadsheet title and compares it to GoogleSheets:ExpectedSpreadsheetName. If the names do not match, or if the API call fails after 3 retries, the application logs the error and exits without processing any files. This prevents writing data to the wrong spreadsheet when SpreadsheetId is misconfigured.