How can I fill a PDF box that will not accept typing?

If a PDF box will not accept typing, first check whether it is a supported text field, a read-only field, or just a box printed on a flat page. In SignDocs, supported standard fields can be filled, while a blank area on a flat or scanned page can receive new text. Read-only restrictions remain. A missing keyboard alone does not tell you which case you have.

Check the source before choosing a workaround

Open the intended PDF from Files and check its title and page count. Download a cloud-only file while connected. If you opened a previously completed, flattened copy, return to the unchanged original: the completed output does not preserve interactive fields for further filling. The original-file restart guide explains how to replace an incorrect completed copy.

Next, read the question beside the box. A checkbox, radio button or choice list expects a selection rather than ordinary typing. SignDocs supports those standard controls as well as text fields. A rectangular outline alone does not establish a text input.

Choose the appropriate next step

1. A supported text field: select it and enter the answer. Check the last visible characters as well as the beginning. Existing field positions stay fixed; filling a field does not move it or change the underlying question.
2. A field known to be read-only: leave its restriction in place. If its value needs changing, ask the sender for a corrected or fillable source. Adding text over the value would leave the earlier information underneath.
3. A blank printed box on a flat page or scan: place new multiline text in the empty answer area, then move and resize the addition to fit. Use a new checkmark for a printed checkbox when appropriate. This adds content; it does not turn the box into an interactive field.
4. An uncertain or unsupported field: do not conclude that it is flat simply because it does not respond. Ask the sender for a standard fillable version or confirm that a manually completed copy is acceptable. No unlocking or automatic field detection is established for SignDocs.

The form-filling guide covers normal completion. For the printed-box branch, use the flat-PDF text guide to check wrapping and overflow.

Example: a workshop form with three kinds of box

Suppose the name field accepts text, the organizer's reference is read-only, and the equipment request is a blank area on a scanned attachment. Type the name into its field. Leave the reference unchanged; request a corrected source if it is wrong. Place the equipment answer on the scanned page and read its final line at a usable size. Do not cover the next question to make the answer fit.

Before saving, check that each answer belongs to its question. Save a separate completed PDF and reopen it from Recent Docs. Compare the name, reference and equipment answer with the source and inspect all pages. The output is flattened, so keep the unchanged original for another attempt. Review the actual attachment before sending.

Built-in option and limits

Apple Preview on iOS 26 may meet the need without another installation. Open the PDF, select Form Filling, select a field and type. Apple also documents adding a text form box when direct filling is unavailable; these are Apple instructions, not SignDocs button names.

SignDocs is useful when you want local form completion alongside handwriting captured from paper. It requires iOS/iPadOS 26 or later, and free completed exports are limited. Processing happens on device without an account or document upload for processing. Installation, purchases/restores, cloud retrieval and external sharing have separate connection requirements. New text does not edit existing page text, provide OCR or remove read-only restrictions.

Product source: Signature Scan: Sign PDFs — App Store