First, check where the process stops
Consider this fictional example: a supplier sends a hosting invoice, but clicking the attachment only brings up a blank preview. That does not tell you whether the file itself is faulty or your email service cannot display it. Start by trying to open the file saved on your computer.
If you were expecting the invoice and have verified the supplier, download the original PDF to your computer. Open the saved file in an up-to-date PDF reader, such as Adobe Acrobat Reader. Adobe recommends this approach for problems viewing PDFs in a browser. If the document opens, check every page to make sure the content is readable. You can then leave the preview problem aside.
If the message looks suspicious or your email service displays a security warning, stop trying to download the attachment. Use contact details you already have for the supplier to check that they sent it, and give them the exact wording of the warning. Do not disable your computer’s protection to access the attachment.
Source for this section: Adobe: what to try when a PDF will not open
Match the symptom to the next step
Make a note of where the process stops and what the application actually says. A missing password calls for a different request to the supplier than a file that remains unreadable. Use the table to choose your next step; an error on its own does not reliably identify the cause.
| What happens | What to try or check | When to contact the supplier and what to ask |
|---|---|---|
| The email preview does not work | For an expected attachment with no security warning, open the downloaded original PDF in an up-to-date reader. | If the saved copy will not open, follow the row about passwords or unreadable downloaded PDFs. |
| The reader asks for a password before showing the document | Check the document’s instructions and the agreed way of obtaining the password. | If the password is missing or does not work, request access instructions through a secure channel. |
| The downloaded PDF will not open or reports damage | If there is no security warning or password prompt, download the original attachment once more. | If the problem persists, ask for a fresh export of the same invoice from the original system. |
| The PDF opens, but a page is missing or the text is unreadable | Check the whole document and identify the page or section that is missing or cannot be read. | Describe the specific problem and ask for a complete, readable copy. |
| Gmail does not allow the download | Distinguish confidential mode from a security message; record the exact wording of any message. | For confidential mode, agree a suitable way to share the document. Handle security warnings through a known contact and do not bypass the block. |
A password prompt does not mean the file is damaged
A PDF can require a password to open, or it can restrict particular actions, such as editing and printing. Adobe distinguishes between these two types of protection. If you can read the invoice normally but cannot edit it, that restriction alone does not make the document unreadable. If your accountant needs to carry out a restricted action, ask the supplier for a suitable version.
If the password needed to open the PDF is missing or does not work, first check the supplier’s instructions. If those do not help, ask how you can obtain the password securely. A password issue alone does not mean you need a fresh export of the invoice. Agree with your accountant how to share both the file and access to it; do not send them the login details for your customer account.
A password prompt does not, by itself, mean that an attachment is safe. Gmail, for example, warns that it cannot scan some encrypted attachments for viruses. If you were not expecting the message, verify the sender through a known contact first.
Source for this section: Adobe: opening passwords and restrictions on PDF use · Google: opening and downloading attachments in Gmail
When Gmail will not let you download the attachment
In Gmail, a message’s confidential mode can prevent downloads. Google states that text and attachments cannot be copied or downloaded in this mode. If that is the issue, ask the supplier for a delivery method that allows you to pass the document to your accountant as agreed.
A security message is a different situation. If Gmail detects a virus in an attachment to a message already in your inbox, it blocks the download. However, a message saying that virus scanning is temporarily unavailable is not the same as a virus being detected. Record the exact wording and use a known contact to ask the supplier to check the attachment. Do not bypass the block or send your accountant instructions for doing so.
Source for this section: Google: opening and downloading attachments in Gmail · Google: virus scanning for attachments
If the file is still unreadable, ask for a fresh export
If the attachment still will not open after one fresh download, and there is no password prompt or security warning, explain the problem to the supplier. Ask them to export the same invoice again from their system. Attaching the same file again may not help. For a damaged PDF, Adobe recommends recreating the document from its original source, which the supplier will usually have access to.
Even repeated failures do not prove that the file is damaged. The purpose of requesting a new copy is to get a readable document you can pass to your accountant. Keep the original email so you can trace where the file came from. Do not upload the invoice to an arbitrary online repair or conversion service for a quick fix.
Use the template below for an unreadable file from a verified supplier. Fill in only the details you know and keep only the steps you actually tried. If you cannot read the invoice number, use a known order reference; do not infer an invoice number from the filename. If the file only needs a password, follow the earlier advice on requesting access instructions instead of using this template.
Select the text, copy it into an email and fill in the details in square brackets.
Source for this section: Adobe: what to try when a PDF will not open
Tell your accountant which document is still unusable
Let your accountant know while you are waiting for a usable copy. Identify the supplier and the purchase or a known order reference, and include the current position and the date you requested a replacement. That saves them having to establish why the document is missing from the files you sent.
Returning to the fictional hosting example, if the PDF still failed to open after a fresh download, you could write: “The September hosting invoice for order DEMO-2026-09 has arrived, but the PDF still will not open after another download. I asked the supplier for a fresh export on 28 September 2026. I am waiting for a readable copy and will forward it once it arrives.” For a password-protected file, say that you are waiting for access instructions instead of a fresh export.
A screenshot of one page can help explain the problem, but it does not establish that you have the whole document. Do not automatically treat it as a complete invoice handover. If you still do not have a readable copy, agree the next step with your accountant.
Open the replacement copy before passing it on
Open the new PDF first and check every page. Make sure the content is readable and that the supplier, customer and known invoice or order reference match the purchase you are dealing with. Only then send the file to your accountant. If they already received the unreadable attachment, add a note that this PDF replaces it.
If the document needs a password or you have changed how you share it, check with your accountant that they can open it too. This completes the technical side of the handover: your accountant has a readable file and knows which purchase it relates to. Being able to open the PDF does not, however, confirm that the invoice is correct or suitable for accounting purposes.